{2x+2y=4
{x-2y=11 (+)
2x+x+2y-2y=4+11
3x=15 /:3
x=5
2x+2y=4
2*5+2y=4
10+2y=4 /-10
2y=-6 /:2
y=-3
Solution: (5; -3)
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