Verified answer

3х+5у=12

х-2у=-7

х=2у-7

6у-21+5у=12

11у=33

у=3

х=6-7

у=3

х=-1

ответ (-1;3)

Verified answer

x=-7+2*y => 1) 3*(-7+2*y)+5*y=12 =>
=>  -21+6*y+5*y=12
       11*y=33
        y=3
        x=-7+2*3=-1