Answer:
4x-12 or 4(x-3)
Step-by-step explanation:
9x+9+2x-7(3+x)
9x+2x+9-21-7x
11x-12-7x
11x-7x-12
4x-12
-15
-10+-9=-19+4=-15
12
8.x-13=3+4.x
8.x-13=7.x
x-13+8=7.x
x-5=7.x
x-x=7+5
x-x=12
x=12