To solve the system of equations using substitution or elimination, let's first solve one of the equations for either variable and substitute it into the other equation.
We'll solve the first equation for x:
x + y = 5
x = 5 - y
Now, we substitute this expression for x into the second equation:
(5 - y) - 5y = -7
5 - y - 5y = -7
5 - 6y = -7
Next, we solve for y:
-6y = -7 - 5
-6y = -12
y = (-12) / (-6)
y = 2
Now that we have the value of y, we substitute it back into the first equation to solve for x:
x + 2 = 5
x = 5 - 2
x = 3
Therefore, the solution to the system of equations is x = 3 and y = 2.