Question

What's the answer on number 11

Answer 1

2x-y=7
2x+7y=31 |* (-1)
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2x - y = 7
-2x-7y=-31
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-y-7y=-24
-8y=-24 |:(-8)
y=3

2x-y=7
2x-3=7 |+3
2x=10 |:2
x=5

x=5
y=3