'how do you solve the y-8x=66, 9y+x=10 with the substitution method
rewrite either equation in a form that shows a single unknown on one side of the equal sign.
y-8x=66
y=66+8x
now substitute this value for y in place of the y in the second equation
9y+x=10
9(66+8x)+x=10
594+72x +x =10
73x = -584
x = -8
now put the found value of y back into the first equation and solve for x
y-8x=66
(-8) -8x = 66
-8x = 66+8
-8x = 74
-x = 9.25
x = -9.25