Question

x+10=y-10 e 2(x-10)=y

Answer 1

x + 10 = y - 10 
2(x - 10 ) = y
2 x - 20  = y

x + 10 = y - 10
x + 10 = 2 x - 20 - 10
x + 10 = 2 x - 30
x - 2 x = -30 - 10
-1 x = -40 
x = -40/-1
x = 40 substituindo o valor de x
x + 10 = y - 10
40 + 10 = y - 10
50 + 10 = y
y = 60