3 - y2 + 7 for y = 5

{3(2x-y)-5(x+y)=-7

{2(x+4y)-5y=5

6x - 3y -5x - 5y=-7

2x + 8y - 5y = 5

x -8y = -7

2x + 3y = 5

x = -7 + 8y

2(-7 + 8y)+ 3y = 5

-14 + 16y + 3y = 5

19y = 5 + 14

19y = 19

y = 1

x = -7 + 8 * (1)

x = 1

Ответ (1; 1)