Answer:
(x + y)(12 + b)
Explanation:
12x + 12y + bx + by
Factorize the first two terms and the last two terms separately (the bracket created should always be the same):
12(x + y) + b(x + y)
The two brackets have now been found. The first bracket is the common factor of (x + y). The second bracket is the factorized terms outside of each bracket (12 + b):
(x + y)(12 + b)