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## 5th grade

### Unit 13: Lesson 1

Writing expressions# Evaluating expressions with & without parentheses

CCSS.Math:

Sal evaluates an expression with and without parentheses. Created by Sal Khan.

## Want to join the conversation?

- can you please show more examples because those two were helpful and i did understand it but it is still pretty confusing(11 votes)
- why does the math seem easier in the videos than in reality(5 votes)
- Because the people who makes the videos know how to do math really good.(13 votes)

- why is math so easy in videos(5 votes)
- Isn't this basically Bidmas??(5 votes)
- Yes, that's exactly what it is. You follow order of operations rules.(0 votes)

- what is { } im still trying to know?(5 votes)
- For parentheses, we use regular parentheses ( ); curly brackets { }, and also square brackets [ ].

Hope this helps.(0 votes)

- 1-(4-2x12)+7 in that problem,inside the parentheses, do i do the multiplication first, or the subtraction?(3 votes)
- you do the multiplication, because you have to do PEMDAS(2 votes)

- So, I understand the situation between parentheses placement and also the order of operations afterward. My question is...when you were doing the second equation, there was a point where you had 8-3x8-3, you did 3x8 to start out, per order of operations. I’m curious how you can differentiate between 3x8 and -3x8 because when I look at this problem, I would’ve automatically connected the negative sign with the 3 being that there wasn’t any parentheses. What is the proper way to go about this?(3 votes)
- Can you please give more examples it would really help me thank you(4 votes)
- Example: (10 x 6) - 5

1.) Solve what is in parentheses first: 60 - 5

2.) Then, subtract: 55(0 votes)

- so in this,you basically solve the problem in the paretheses and then solve the problem outside the paretntheses with the answers of both.Am i correct?(2 votes)
- yes correct. you do the parentheses first then you go from left to right and solve the problem.(3 votes)

## Video transcript

What I want to do is think about
whether this expression right over here would evaluate
the same way whether or not we had parentheses. So to think about
that, let's first think about how
it would evaluate if we add the parentheses. So if we add the
parentheses, we want to do what's ever in
the parentheses first. And so here we have 8 minus
3, which is equal to 5. So this simplifies to 5
times 5 times 8 minus 3. And now we want to
do the multiplication before we do subtraction. This goes back to
order of operations. You do your multiplication
and division first. Well, you do your
parentheses first. Then if you have multiplication,
division, addition, and subtraction
all in a row, you want to do your multiplication
and your division first. So here we're going to
multiply 5 times 8 to get 40, and then we're going to
subtract 3 to get 37. Now, let's think about
what this would evaluate to if we did not
have the parentheses. So it would be 8 minus
3 times 8 minus 3. So we just have to
remind ourselves about the order of operations. The convention is to do
your multiplication first. So you're actually going to
multiply the 3 times the 8 before you subtract
it from this 8 and then before you
subtract this 3. So we took away the parentheses,
but the order of operations say, hey, do this
multiplication first. We could even put a parentheses
here to emphasize that. So this will become
8 minus 8 minus 24. Let me write it this way. 8 minus 24 minus 3. 8 minus 24 minus 3. Now, 8 minus 24 is negative 16. You subtract another 3, you're
going to get to negative 19. So clearly, you get very,
very different values depending on whether or
not you have parentheses.