we have
-12(x-12)=-9(1+7x)
Apply distributive property both sides
-12x+144=-9-63x
Group terms
63x-12x=-144-9
51x=-153
x=-153/51
x=-3
Part 21
we have
20=5(-3+x)
First way
Apply distributive property right side
20=-15+5x
adds 15 both sides
20+15=5x
35=5x
Divide by 5 both sides
x=35/5
x=7
Second way
20=5(-3+x)
divide by 5 both sides
20/5=