Question

Solve 12x = 4(x + 5)

Answer 1

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
$x= \frac{20}{8}= 2 \frac{4}{8}=2.5$

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