Respuesta :

Hello There!

Put it into an equation:

3 (x + 3) = x + 15
Expand it:
3x + 9 = x + 15
     - 9         - 9
3x = x + 6
- x    - x
2x = 6
Divide by 2:
x = 3

Hope This Helps You!
Good Luck :)