You cannot.
LCM{2,6,12} = 12 and GCF{2,6,12} = 2
LCM{4,6,12} = 12 and GCF{4,6,12} = 2
The two sets have the same LCM and GCF but, clearly, their sums are different.
The sum is 84 and the GCF is 6
3 (21+5)
The Greatest Common Factor is 3
2(24 + 7)
The sum is: 5+1 = 6
The GCF is 7.
They are: GCF = 5 and LCM = 325 and the sum is 5+325 = 330
The sum is 335.
The sum is 84 and the GCF is 6
9(2 + 3)
3 (21+5)
11(5 + 6)
5(8 + 5)
9(2 + 3)
7(7 + 9)
This question requires more information in order for it to make any sense at all! You cannot have a sum of a number: you need two or more numbers. A single number cannot have a GCF. The GCF needs to be COMMON to two or more numbers.
The GCF of 75 and 90 is 15.