Given:
9 = 3x + 9 - 15x
Let's combine the like terms:
Here, 9 and 9 are like terms while 3x and 15x are like terms since they have same variable x
9 = 3x + 9 - 15x
Take The 9 on the left hand side of the equation to the right hand side(it changes to negative 9)
= 3x + 9 - 15x - 9
Collect like terms:
= 9 - 9 + 3x - 15x
= 0 - 12x
= -12x
