Answer:
3(3b +4)
Step-by-step explanation:
The greatest common factor (GCF) of 9 and 12 is 3, so you're being asked to factor that out.
9b +12 = 3(3b +4)
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The GCF can be found a couple of ways. One of them is to list the prime factors and identify those that are common.
9b = 3 × 3 × b
12 = 2 × 2 × 3
For these two terms, the only common factor is 3.