Answer:
Step-by-step explanation:
AB + BC = AC
9x + 7 - 3x + 20 = 39 { combine like terms}
9x -3x + 7 + 20 = 39
6x + 27 = 39 {Subtract 27 from both sides}
6x = 39- 27
6x = 12 {divide both sides by 6}
6x/6 = 12/6
x = 2
