Answer:
(x + 3b)(3 + 5a)
Step-by-step explanation:
Assuming you require the expression factorised.
Given
3x + 9b + 5ax + 15ab ( factor the first/second and third/fourth terms )
= 3(x + 3b) + 5a(x + 3b) ← factor out (x + 3b) from each term
= (x + 3b)(3 + 5a) ← in factored form
