Just use elimination
Steps:
1. Multiply everything in the system 7x-y=3 by 2
2. New systems are
3x + 2y=11
14x-2y=6
3. 2y + -2y= 0 so y cancels itself out
4. 14x+ 3x=17x
11 + 6=17
5. New problem is
17x=17
6. Divide each side by 17
7. Your answer is x=1
8. Now substitute the x in 7x-y=3 for 1
7(1)-y=3
7-y=3
9. Subtract 7 on both sides
-y=-4
10. Divide by -1
y=4