We have the system:
x + 5y = 20
2x - 7y = -45
Using the elimination method, we'll have
x+ 5y = 20 *(-2)
2x - 7y = -45
-2x -10y = -40
2x -7y= -45
Adding the equations:
-17y = -85
y = 5
So:
2x - 7*5 = -45
2x - 35 = -45
2x = -45+35
2x = -10
x= -5
Solution: S= {-5,5}
