Cant figure out what to do (equations)

Question

1)Find three consecutive even integers with a sum of -30

2)Find four consecutive integers with a sum of 26

Answer 1

n-2, n, n+2
n-2 + n + n+2 = -30
3 n = -30
n=-10
so
-12 , -10, -8
=======================
n + n+1 + n+2 + n+3 = 26 etc

Answer 2

I get it but why do we do n-2?

Answer 3

The second one equals to 32

Answer 4

I did n-2 to get n in the middle so I would get a simple 3n on the left. I could just as well have used:
n + n+2 + n+4
or
n-4 + n-2 + n

Answer 5

Also notice that the fact that it is odd or even is not used. Luckily it comes out with n even.