looks like the first thing you have to find is their GCF, ya reckon ? The factors of 56 are 1, 2, 4, 7, 8, 13, 28, and 56 . The factors of 64 are 1, 2, 4, 8, 16, 32, and 64 . The common factors are 1, 2, 4, and 8 . The greatest one is 8 . 56/8 = 7 64/8 = 8 56 plus 64 = (8 times 7) plus (8 times 8) 56 plus 64 = 8 times (7 plus 8) <== that's the answer Check it out: 56 plus 64 = 120 8 times (7 plus 8) = 8 times 15 = 120 yay!