Question

find all possible pairs of two natural numbers whose sum is 77 and their gcd is 7

Answer 1

7+ 70,21+56,35+42,49+28,

Answer 2

With these specifications, we need to list the divisors of 7 from 7 to 77

The divisors of 7 are:

7,14,21,28,35,42,49,56,63,70,77

Lets now see which pair will give us 77..

We proceed:

7+70
21+56
63+17
56+21
49+28
35+42

All these pairs give us 77.