Method 1:

Factor the each monomial.

32mn² = 2 · 2 · 2 · 2 · 2 · m · n · n

16n = 2 · 2 · 2 · 2 · n

12n³ =  2 · 2  · 3 · n · n  · n 

The GCF is the product of the common prime factors in each monomial.

GCF = 2 · 2 · n  = 4n

The greatest common factor of 32mn²,16n and 12n³ is 4n.

The greatest common factor of 32mn²,16n and 12n³ is 4n.