Answers by visitors named: Equinox

Adding a negative integer is the same as subtracting a positive one. For example: 1+(-2)= 1-2 That makes the answer to the example -1. The priniple also applies to your problem.

If the positive number is larger than the negative number, the result will be positive. If the negative number is larger, the result will be negative.

The control group is there to provide something to be compared to