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One-step addition equation

Learn how to solve this equation: a + 5 = 54 . Created by Sal Khan.

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  • duskpin seed style avatar for user wilson.gianna
    why is there a pic of queen Elizabeth just chillin'?
    (43 votes)
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  • piceratops tree style avatar for user Ali Flynt-Oronde
    Why do some numbers get canceled out?
    (6 votes)
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  • blobby green style avatar for user sloank5789
    Is this going to be easy
    (6 votes)
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  • blobby green style avatar for user nadeemk2284
    what do you do if the variable is in the midlle of both numbers for example -10.74=u- (-11)
    (5 votes)
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    • stelly blue style avatar for user Kim Seidel
      Does it help you is you change the equation around?
      u-(-11) = -10.74
      You can switch the sides of an equation. Now the "u" is not in the "middle" of the numbers. Though, I would argue it was never in the middle of the numbers because the equals symbol is really separating the "u" from the number on the left side.
      (3 votes)
  • leaf blue style avatar for user Rylee Ostanik
    why is this different then what the screen shows when you get it wrong and hit the help button?
    (4 votes)
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  • old spice man blue style avatar for user IZICKFRELIGH
    and we can do this another way the awnser is 49
    (5 votes)
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  • blobby green style avatar for user CAMILA ARTILES
    How do I fix an equation like 44-q = 11 It's simply a true / false answer in my pre-algebra book. The answer is simple, it's 33. However, I do not know how to configure the equation. The example in the video shows the variable minus the number equals the difference. But what happens when the number is first and the variable is subtracted from the number? How can I configure this equation so that future equations that can not simply be solved without showing the work can be solved?
    (3 votes)
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    • stelly blue style avatar for user Kim Seidel
      You have 2 options...
      Option 1
      Subtract 44 from both sides: -q = -33
      Then, you need to divide both sides by -1 to change -q into just q: q = 33

      Option 2
      Add q to both sides: 44 = 11 + q
      Then subtract 11 from both sides: 33 = q

      Hope this helps.
      (2 votes)
  • aqualine tree style avatar for user Eunice Huang
    why do you need to subtract or add numbers to both sides when you are just getting number off from one side?
    (2 votes)
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    • stelly blue style avatar for user Kim Seidel
      If you just do the operation to one side, the equation is no longer equal (in balance).
      For example: 2+5 = 11-4
      I've used only numbers so you can see both sides currently = 7. The equation is in balance.
      Add 4 to only right side and you get: 2+5 = 11
      The equation is no longer equal. I've performed an invalid operation to the equation.

      Note: Some teachers teach that you pick up the number and move it to the other side by changing its sign. For example, change the "-4" into "+4" and put it on the left side:
      2+5+4 = 11
      But, to achieve this, you still have added 4 to both sides. It was just not written out.
      Hope this helps.
      (2 votes)
  • male robot hal style avatar for user Rahul Dalvi
    At what did he mean
    (2 votes)
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  • blobby green style avatar for user Jaie Aron
    would we do the same if it is a negative number?
    (2 votes)
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Video transcript

Solve for a and check your solution. And we have a plus 5 is equal to 54. Now, all this is saying is that we have some numbers, some variable a. And if I add 5 to it, I will get 54. And you might be able to do this in your head. But we're going to do it a little bit more systematically. Because that'll be helpful for you when we do more complicated problems. So in general, whenever you have an equation like this, we want to have the variable. We want this a all by itself on one side of the equation. We want to isolate it. It's already on the left-hand side, so let's try to get rid of everything else on the left-hand side. Well, the only other thing on the left-hand side is this positive 5. Well, the best way to get rid of a plus 5, or a positive 5, is to subtract 5. So let's subtract 5. But remember, this says a plus 5 is equal to 54. If we want the equality to still hold, anything we do to the left-hand side of this equation, we have to do to the right side of the equation. So we also have to subtract 54 from the right. So we have a plus 5 minus 5. Well, that's just going to be a plus 0. Because if you add 5 and you subtract 5, they cancel out. So a plus 0 is just a. And then 54 minus 5, that is 49. And we're done. We have solved for a. A is equal to 49. And now we can check it. And we can check it by just substituting 49 back for a in our original equation. So instead of writing a plus 5 is equal to 54, let's see if 49 plus 5 is equal to 54. So we're just substituting it back in. 49, 49 plus-- let me do that in that same shade of green. 49 plus 5 is equal to 54. We're trying to check this. 49 plus 5 is 54. And that, indeed, is equal to 54. So it all checks out.