Answer:
subtracting one from the other
Step-by-step explanation:
The equations are not well written. Let us assume the equations are:
2x + y = 7 .... 1
2x + 2y = 5 ....2
Looking at the two equations, using elimination method will be the best way to go.
Since the coefficient of the variable x are the same, we can take the difference of both equation to cancel out the variable x and get y as shown;
(2x-2x) + (y-2y) = 7-5
0 - y = 2
y = -2
Note that you can only subtract if the coefficient of the variables in both equations have the same coefficient (same sign) and add if they have different signs