Subtracting a negative number is the same as adding the positive.

The answer may be positive or negative depending on the size of the numbers.

Examples

15 - -21 = 15 + 21 = 36

-117 - -30 = -117 + 30 = -87

Remember

-11 + 3

is the same as

 3 + -11

which is the same as

 3 - 11

which is -8