Question

I'm not sure how to make the -4 positive

Answer 1

Depending on your situation, to make any negative number positive, you can add its positive version to it(like -2 you would do -2 +2). If you want to make its positive number equal you would multiply it in its negative state by 2 (-5 x 2= 5).

Answer 2

You have to multiply it by a negative number.