Answer
14
Work Step by Step
The GCF is the biggest factor (divides a number evenly, with no remainders or left overs) that all numbers in a group or sequence are divisible by.
First, list all the factors.
Then, multiply the factors all the numbers have in common. That is the GCF.
42 = 7 $\times$ 2 $\times$ 3
28 = 7 $\times$ 2 $\times$ 2
7 $\times$ 2 = 14
14
