{7x+15y=32 {x-3y=20 /*5
{7x+15y=32
{ 5x-15y=100 (+)
7x+5x+15y-15y=32+100
12x=132 /:12
x=11
x-3y=20
11-3y=20 /-11
-3y= 9 /:(-3)
y=-3
The solution: (11; -3)