Question 213529
3x - y = 7 multiply by -2 & add

2x - 2y = 2
-6x+2y=-14
------------------
-4x=-12
x=-12/-4
x=3 ans.
3*3-y=7
9-y=7
-y=7-9\-y=-2
y=2 ans.
Proof:
2*3-2*2=2
6-4=2
2=2