Question

Resolva
a- (-15) + (+9)
b- (-9) +(+9)
c- (+15) + (-15)
d- 0 +(+20)

Answer 1

a = -6
b = 0
c = 0
d = 20

Grava esse esqueminha 

- - = +
- + = -
+ + = +
+ - = -

Answer 2

a) - 6
(- 15) + (+ 9) =
= - 15 + 9 =
= - 6

b) 0
(- 9) + (+ 9) =
= - 9 + 9 =
= 0

c) 0
(+15) + (- 15) =
= 15 - 15 =
= 0

d) 20
0 + (+ 20) =
= 0 + 20 =
= 20