12x=4(x+5) (multiplying 4 by each argument in the parenhesis)
12x=4x+20 /-4x both sides
8x=20 /:8 divide both sides by 8
[tex]x= \frac{20}{8}= 2 \frac{4}{8}=2.5 [/tex]
15x-3(3x+4)=6 (-3 times each argument in the parenthesis)
15x-9x-12=6
6x-12=6 /+12 both sides
6x=18 /:6 divide both sides by 6
x=3
3x-5x+10=36
-2x+10=36 /-10 both sides
-2x=26 /:(-2) divide both sides by -2
x=-13
2(x+3)=x+10
2x+6=x+10 /-x
x+6=10 /-6
x=4