The greatest common factor (GCF) of 49 and 63 is: 7
To find the GCF, you simply gather up the factors for both of the numbers, but make sure you only write out the factors that are less or equal to 49, since you shouldn't go over the minimum number.
Factors of 49: 1, 7, 49
Factors of 63: 1, 3, 7, 9, 21
Now that we know the factors of both of the numbers, we should find the most common between them. Which numbers are common between the two numbers? The common factors of them are 1 and 7, but we are looking for the greatest common factor. Now, which is the greatest of 1 and 7? It is 7, since 7 is a higher number than 1.