Use the substitution method to solve this simultaneous equation.
Rewrite one of the equations as y=... and then substitute this into the second equation everytime y occurs.
Find out what x or y equals in one of the equations and then substitute it into the second equation. This gives you the value of one variable. Then just plug that value into one of the original equations to find the other variable:
EX:
x + y = 10
2y - 2x = 0
x = -y + 10
2y - 2(-y + 10) = 0
2y + 2y - 20 = 0
4y = 20
y = 5