Multiply both sides of the first equation by 2 to get:
2x + 4y = -24
2x + y = 20
subtract second equation from first to get:
3y = -44
divide both sides of equation by 3 to get:
y = -44/3
Replace y with -44/3 in first equation to get:
x+2y = -12 becomes:
x + 2*(-44/3) = -12
which becomes:
x - 88/3 = -12
multiply both sides of this equation by 3 to get:
3x - 88 = -36
add 88 to both sides of this equation to get:
3x = 88 - 36 = 52
divide both sides of this equation by 3 to get:
x = 52/3
you have:
y = -44/3
x = 52/3
Replace x and y in both original equations to confirm these answers are good.
x+2y = -12
y = 20-2x
become:
52/3 + 2*(-44/3) = -12
-44/3 = 20 - 2*(52/3)
first equation becomes 52/3 - 88/3 = - 12 which becomes -36/3 = -12 which becomes -12 = -12 which is true so the value for x and y are good.
second equation becomes -44/3 = 20 - 104/3 = 60/3 - 104/3 = -44/3 which is also true so the value for x and y are good in both equations.
