Answer:
Step-by-step explanation:
Factor both numbers into their prime factors. Then pick the numbers that are in both.
42: 2*3*7
63:3*3*7
Which numbers are in both rows.
3 and 7
One more example would be good.
Suppose the two numbers were
45: 3*3 * 5
63:3 *3 * 7
In this example, there are two threes in both numbers. Both of them must be used for the GCF: 3*3 = 9
The GCF = 21 for your question.
