Solve for both systems: - 3x - y = - 31 and 5x + y = 51

- 3x - y = - 31

- 3x - y +y= - 31+y

-3x=-31+y

-3x+31=-31+31+y

-3x+31=y

5x + y = 51

5x -3x+31= 51

-2x+31= 51

-2x+31-31= 51-31

-2x=20

-2x/-2=20/-2

x=-10

-3x+31=y

-3(-10)+31=y

30+31=y

61=y