I never really understood it either usually I just this (-3+7) as you can tell the (-3) is smaller so I just move it to the other side and I see it as 7-3 which is the basic math and when it get more complicated like 27+(-87) I just do this 27-(87) and I move the smaller # (27) to the left side and now I have -87+27 and I change that to -87-(-27) which would equal -60 it seems a bit complicated and like a lot of procedures but I tried to explain it as best as possible
