7 + - 0 + - 9 + - 9 + - 5 + 7 = - 9

Can someone give me the steps on how I'm supposed to find - 9 as the answer? Anything's greatly appreciated.

7 + - 0

7 - 9

-2 - 9

-11 - 5

-16 + 7

A = - 9

Addition is commutative: a + b = b + a, so we can solve it like this:

7 + - 0 + - 9 + - 9 + - 5 + 7 =

= 7 + 7 + - 5 + - 9 + - 9 =

= 14 + - 5 + - 9 + - 9 =

= 9 + - 9 + - 9 =

= - 9

Or in similar way which makes it easier.

We can also count as it is, from left to right:

7 + - 0 + - 9 + - 9 + - 5 + 7 =

= 7 + - 9 + - 9 + - 5 + 7 =

= - 2 + - 9 + - 5 + 7 =

= - 11 + - 5 + 7 =

= - 16 + 7 =

= - 9