Which correctly shows how to use the gcf and the distributive property to find an expression equivalent to 45 + 72? 3(15 + 24) 9(5 + 8) (5)(9) + (2)(36) (3)(15) + (8)(9)

First find the GCF of 45 and 72
45=3^2*5
72=2^3*3^2
The GCF is the greatest common factor between the two numbers (or expressions).  In this case, the GCF is 3^2=9.

Next, breakdown 45 and 72 into products in which GCF=9 is a factor,
45=9(5)
72=9(8)

Finally, add the two expressions, and factor
45+72=9(5)+9(8)=9(5+8)