Solve the equation: 18x + 9x = 33 + 21.

Solution:

1. Combine like terms on both sides of the equation:
• Left side: 18x + 9x = 27x
• Right side: 33 + 21 = 54
2. The equation becomes: 27x = 54
3. Isolate x by dividing both sides by 27:
• x = 54 / 27
• x = 2

Answer: x = 2