Given: 8x-9y=128x−9y=12. Solve for x.
8x-9y+9y=12+9y8x−9y+9y=12+9y
8x=12+9y8x=12+9y
(8x)/8=(12+9y)/88x8=12+9y8
x=(12+9y)/8x=12+9y8
Substitute this into the other equation:
-8x+3y=12−8x+3y=12
-8((12+9y)/8)+3y=12−8(12+9y8)+3y=12
-1(12+9y)+3y=12−1(12+9y)+3y=12
-12-9y+3y=12−12−9y+3y=12
-12-6y=12−12−6y=12
-12-6y+12=12+12−12−6y+12=12+12
-6y=24−6y=24
(-6y)/-6=24/-6−6y−6=24−6
y=-4y=−4
Substitute into original equation:
8x-(9*-4)=128x−(9⋅−4)=12
8x+36=128x+36=12
8x+36-36=12-368x+36−36=12−36
8x =-248x=−24
(8x)/8=-24/88x8=−248
x=-3x=−3
To check, substitute both answers into both the formulas:
-8*-3+3*-4=24-12=12−8⋅−3+3⋅−4=24−12=12 True
8*-3-9*-4=-24+36=128⋅−3−9⋅−4=−24+36=12 True