A coprime pair of positive integers are two which have
no factors in common other than 1.
A composite integer has three or more factors.
We prime factor 80:
80 = 8*10 = 2*2*2*2*5
Pick an integer that has at least 3 factors, in order to
be composite, that doesn't have either 2 or 5 as a factor.
The smallest one we could pick would be 3*3 = 9, it has
three factors 1,3,and 9. Or we could pick 3*7 or 21. It
has 4 factors 1,3,7,and 21. (80,9) is a coprime pair.
So is (80,27).
Edwin
