So just plug in the numbers (x,y) into the equations.
A) (7.5, -5)
2(7.5) -5 = 10
15 - 5 = 10 yup, this works.
Let's see if it works for other equation.
-2(7.5) + 2(-5) = 5
-15 - 10 = 5 nope, this does not work.
B) (-2.5, -5)
2(-2.5) - 5 = 10
-5 - 5 = 10 nope, doesn't work
Since it doesn't work we don't need to try for other equation.
C) (2.5, 5)
2(2.5) + 5 = 10
5 + 5 = 10 yup, this works.
Now the other equation.
-2(2.5) + 2(5) = 5
-5 + 10 = 5 and this works.
So the solution to this set is answer choice C