Find the GCF of 42m−28n .

To find the greatest common factor (GCF) of 42m and 28n, we need to find the largest number that can divide both 42m and 28n evenly.

First, let's factor out 42m:
42m = 2 * 3 * 7 * m

Next, let's factor out 28n:
28n = 2 * 2 * 7 * n

Now we can identify the common factors between the two expressions:
The common factors are 2, 7, and m.

To find the GCF, we multiply the common factors together:
GCF = 2 * 7 * m = 14m

Therefore, the GCF of 42m and 28n is 14m.