Answer:
Step-by-step explanation:
hello :
a(x) = 3x - 12 and b(x) = x-9, so
a[b(x)]=a(x-9) =3(x-9)-12
a[b(x)]=3x-9-12
a[b(x)]=3x+21
65/5
You just need to multiply 13 by 5.
