Hello!
Let's set up some things:
<-- equation 1
<-- equation 2
________________
(equation 1) multiplied by 2
<-- equation 3
________________
(equation 2) - (equation 3)
7y = 0
y = 0 <-- equation 4
________________
(equation 4)'s value of y into (equation 1)

Thus x = 5 and y = 0
Hope that helps!