Question

x+y = 90
x-y = 10
resolvam pessoal obrigado.

Answer 1

x+y = 90
x-y = 10

x = 10 + y

10 + y + y = 90
10 + 2y = 90
2y = 90 - 10
2y = 80
y = 80/2
y = 40

x = 10 + y
x = 10 + 40
x = 50