Which expression shows 28 + 35 as the product of their greatest common factor and the sum of two whole numbers with no common factor?

a. 7(6 + 3)
b. 9(4 + 3)
c. 7(4 + 5)
d. 9(2 + 5)

Step-by-step explanation:

we have

we know that  

and that

so the number 7 is their greatest common factor, thus instead of we can write the following:

and taking the common factor out:

we get that the answer that is the product of the greatest common factor (7) and the sum of two whole numers (4+5) is opction C.