left { {{4x-y=9} atop {3x+7y=-1}} rightleft { {y=4x-9} atop {3x+7(4x-9)=-1}} right. . \
3x+28x-63=-1\
31x=62\
x=2\
y=4*2-9\
y=-1\
Ответ:(2;-1)