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:
57=5+(7)-5\goldD{-7} = -5\goldD{+(-7)}
10(3)=10+310\goldD{-(-3)}=10\goldD{+3}
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 - negative

Lets subtract 5(6)-5-(-6).
Step 1: Rewrite as an addition problem
5(6)=5+6-5\goldD{-(-6)}=-5\goldD{+6}
Step 2: Start at the first number in the addition problem, in this case 5-5:
Step 3: Move 66 places to the right. We move 66 to the right because adding positive 66 increases our number by 66.
5+6-5+6 takes us to 11 on the number line.
5(6)=1-5-(-6)=1

Example 2: negative - positive

Lets subtract 47-4-7.
Step 1: Rewrite as an addition problem
47=4+(7)-4\goldD{-7}=-4\goldD{+(-7)}
Step 2: Start at the first number in the addition problem, in this case 4-4:
Step 3: Move 77 places to the left. We move 77 to the left because adding negative 77 decreases our number by 77.
4+(7)-4+(-7) takes us to 11-11 on the number line.
47=11-4-7=-11
Want to learn more about subtracting negative numbers? Check out this video.

Practice

Want to try some more subtracting negative numbers problems? Check out this exercise.