1) what is 54+63? it's 117!
2) what is their gcf? well, they''re both divisible by 9:
54=9*6
63=9*7
and 6 and 7 have no divisors in common other than 1, so gcf is actually 9!
so what is 117 as a sum of 9 and something else?
the something else s 117-9=108
so the answer is 9+108