Solve.

5. x + 6 + 2x = 15

x + 6 + 2x = 15

x+2x+6 = 15 (combine like terms)

3x+6 = 15

move + 6 to the other side

sign changes from + 6 to - 6

3x+6-6 = 15-6

3x = 15-6

3x = 9

divide both sides by 3 to get x by itself

3x/3 = 9/3

Cross out 3 and 3, divide by 3 and then becomes 1*1*x = x

x = 9/3

Answer: x = 3