If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

## Operations and Algebraic Thinking 218-221

### Course: Operations and Algebraic Thinking 218-221>Unit 5

Lesson 3: One-step addition & subtraction equations

# One-step addition & subtraction equations: fractions & decimals

Learn how to solve one-step addition and subtraction equations that have fractions and decimals in them.

## Want to join the conversation?

• This video is good and all, but what if the denominator of the fractions are not the same. Then what do I do then, please explain. Cause I have a problem that doesn't have the same denominator.
• You still move the fraction away from the side with the variable. Then to do the addition/subtraction on the other side, you will need to use the correct steps for adding & subtracting fractions:
1) find a common denominator
2) convert each fraction to the common denominator

If you look at the other questions posted under this video, you will see some examples of problems with different denominators.

Hope this helps.
• distance maybe?
• Does Sal ever get anything wrong?
• Yes - Sal is human. If you watch the videos in regular mode (not full screen), then you will see correction boxes that pop up to correct content in the video.
• Ill give you one to solve. 35= x/7
• You have "x divided by 7" on the right side. To move the 7, you use the opposite operation to division. You need to multiply both sides by 7.
See if you can finish the problem.
Hope this helps.
• What if the denominators are different like 11/6=n+7/9?

Thank you! :3
• I'm horrible with fractions sooooo problem because I do not understand them and that's my problem so can you try to explain it a little better please?
• Hello there!
Fractions are quite easy to solve if you keep yourself reminded that they need a common denominator.
Unlike with multiplication and division, they need the same number on the bottom. For example, 1/4 cannot add or subtract with 1/2, so they need a common denominator.
In the same problem, you could list out the multiples. 4 is a multiple of 2 as well as itself. That means you'd have to make a half 2/4, as they're the same fraction.
If you were adding the problem, you would do 1/4 +2/4 = 3/4.
In this type of addition, they would have something like 1/4 + a =3/4.
You would still have to do the same thing, and switch to an inverse operation.
Hope this helps ^^
(If you have any questions regarding this, I'm always happy to help)
• what if there are 2 different denominators?
• I'll keep the explanation brief while hopefully still adequately covering the basics.

So, I'm looking to simplify a problem. The problem is 7/12 + 3/5. These denominators unfortunately do not match, so I cannot add them immediately. I'll have to find a way to make them match. I can do this by multiplying both numbers of the fraction by a number that matches the two. An easy way to do this is to multiply the fractions by each other's denominators, which is guaranteed to work, but not always simplest form. Now, once I do this, I will have 35/60 + 36/60. Now I can add these, and get 71/60, or 1 11/60.

I hope this helps you!
• If you have X+5=13 you could just subtract 5 from 13 instead of adding or subtracting something to both sides.
• You are just skipping work steps. The property that lets you do what you are suggesting says that you must add/subtract the same value from both sides. You are just skipping the step of writing out that +5-5 = 0 on the left side, which is what makes the 5 disappear on that side.
• This video is good and when i see this video i got little easy