Question

qual o calculo de
x+y=7
2x+y=9

Answer 1

x+y = 7  (-1)
2x+y = 9

-x-y = -7
2x+y=9(subtrai c de 2x, y de y e 7 de 9)
 x=2

x+y=7
2+y=7
y=7-2
y=5

S{2,5};