Main content

## 7th grade (Illustrative Mathematics)

### Course: 7th grade (Illustrative Mathematics) > Unit 5

Lesson 5: Lesson 5: Representing subtraction# Subtracting negative numbers review

Review the basic of subtracting negative numbers and try some practice problems.

## Subtracting negative numbers

Subtracting a number is the same as adding the opposite of the number.

Let's look at two examples:

Note: In both examples, we change subtraction to addition and changed the sign of the second number to the opposite sign.

*Want to know why this works? Check out this video.*

Once we have an addition problem, we can solve.

### Example 1: negative minus negative

Lets subtract minus, 5, minus, left parenthesis, minus, 6, right parenthesis.

Step 1: Rewrite as an addition problem

Step 2: Start at the first number in the addition problem, in this case minus, 5:

Step 3: Move 6 places to the

**right**. We move 6 to the**right**because**adding positive 6 increases**our number by 6.minus, 5, plus, 6 takes us to 1 on the number line.

### Example 2: negative minus positive

Lets subtract minus, 4, minus, 7.

Step 1: Rewrite as an addition problem

Step 2: Start at the first number in the addition problem, in this case minus, 4:

Step 3: Move 7 places to the

**left**. We move 7 to the**left**because**adding negative 7 decreases**our number by 7.minus, 4, plus, left parenthesis, minus, 7, right parenthesis takes us to minus, 11 on the number line.

*Want to learn more about subtracting negative numbers? Check out this video.*

## Want to join the conversation?

- why does it say subtract when you have to add(253 votes)
- Because two negatives equal a positive in a subtraction when it's next to each other. 3-(-6)=9=3+6=9(105 votes)

- Negative minus a positive is a negative?(70 votes)
- Yes, subtracting a positive always makes the number smaller.(51 votes)

- So basically 2 negatives make a positive?(55 votes)
- You could be mistaking this for a multiplication problem. negative * negative = positive but in addition negative + negative = negative.(8 votes)

- So, correct me anyone if I'm wrong. So let's say I have

-4-(-4), wouldn't equal 0? Because instead of me subrtracting with -4, I have to add it. So, would it be 0 instead of -8?(32 votes)- Yes that is correct.(8 votes)

- I am confused that 8 - (-2) means you add up. IS that count Mr.Khan?(16 votes)
- Because when you do a subtraction problem with a positive taken away, you go down. 8 - 2 = 6 When that's negative, you have the
*opposite*, so you go up. 8 - ( - 2 ) = 10 You still might wonder why it isn't - 10, but I can answer it. Subtraction and addition like this stuff are never gonna give you negative.(11 votes)

- why does it add when it says to subtract?(14 votes)
- When you have a double negative, or two negatives in a row, it is the same as having a positive.

2+2 = 2-(-2) there are two negatives in a row so it becomes positive.(11 votes)

- I don't get why they are swiching the signs telling me to add when I have to subtract. I just don't understand at all.(8 votes)
- Another way to think of a negative sign is as an OPPOSITE sign. So when you are subtracting a negative, it's really telling you to do the opposite of subtracting, which ends up being adding.

Another way some people might look at it is to think of someone telling you that you no longer owe them any money you borrowed. By taking away your debt (subtracting a negative), they have given you a gift (adding a positive).(25 votes)

- so two negatives make a positive(5 votes)
- It depends on the operation.

Adding two negatives always makes a negative.

Subtracting two negatives could make zero, a negative, or a positive depending on how the two negatives compare to each other.

Multiplying or dividing two negatives always makes a positive.(5 votes)

- Is there an easier way to solve these without wasting space on a worksheet of paper?(13 votes)
- Just change the sign of the second number and add(11 votes)

- wait so a negative minus a negative is the same as a positive plus a positive?(6 votes)
- you almost got it a negative plus a positve is a negative so say i have -9 dollars and i borrow some from the bank wich is 10 dollars so now i owe the bank 10 dollars so now i have -90 dollars hope this helps(11 votes)