Highest common factor is popularly known as the Greatest Common Factor or GCF.
To look for the GCF:
First, get all the factors of both numbers. Factors are the numbers multiplied with one another. 99 and 63 are products of different factors.
Second, compare the factors of both numbers and select their Greatest Common Factor
1) Get the factors
Factors of 99 are 1, 3, 9, 11, 33, 99
Factors of 63 are 1, 3, 7, 9, 21, 63
2) Identify their common factors which are 1, 3, and 9
Of the three factors, the greatest common factor is 9.
GCF = 9