What is the greatest common factor of 24 72and 132?

gcd(a,b) = greatest common divisor (or factor, whatever) of a and b.

For any set of number, a1, a2, a3, ..., you can use the Euclidean algorithm (http://en.wikipedia.org/wiki/Euclidean_algorithm) to get the gcd(a1, a2), and then again to get gcd(gcd(a1, a2), a3), etc.

Often, though, you can eyeball it. So 24*3 = 72. Therefore, gcd(24, 72)=24. 24 does not divide 132, but 12 does (the next biggest factor of 24), so gcd(24, 72, 132)=12.