So, the sum of numbers will be the result of 36+45, that is 81.
Let's find the GCF: it's at least 9, since both numbers are divisible by 9 (36/9=4; 45/9=5)
so 81 (the sum of the numbers) equals 99 (where 9 is the gfc)
and the answer is 81=(4+5)9, where 4+5 is the "another sum".