x = 9
Step-by-step explanation:
7x + 3x - 18 = 6(x + 3)
10x - 18 = 6(x + 3) Add like terms
10x - 18 = 6x + 18 Distribute 6 to x and 3
4x - 18 = 18 Subtract 6x to both sides
4x = 36 Add 18 to both sides
x = 9 Divide 4 to both sides