Question

{9x-y/7+2y=3
{12x+5y/3-3x=3

Answer 1

{9x-y=21+6y⇒9x-7y=21/*5⇒45x-35y=105
{12x+5y=9-9x⇒21x+5y=9/*7⇒147x+35y=63
прибавим
192x=168
x=7/8
9*7/8-7y=21
7y=63/8-21
7y=-105/8
y=-105/56