To solve this, you need to isolate/get the variable "x" by itself in the equation:
7x - 20 = 3(4 + x) Distribute/multiply 3 into (4 + x)
7x - 20 = (3)4 + (3)x
7x - 20 = 12 + 3x Subtract 3x on both sides
7x - 3x - 20 = 12 + 3x - 3x
4x - 20 = 12 Add 20 on both sides
4x - 20 + 20 = 12 + 20
4x = 32 Divide 4 on both sides
[tex]\frac{4x}{4} =\frac{32}{4}[/tex]
x = 8
PROOF
7x - 20 = 3(4 + x) Plug in 8 for x
7(8) - 20 = 3(4 + 8)
56 - 20 =3(12)
36 = 36
