Question

What are the prime factors of 126

Answer 1

126 equals 2*63, 2*63=2*7*9, 2*7*9=2*3*3*7.  2, 3, and 7 are all prime, so these are the prime factors of 126.

Answer 2

you can use the factor. 
       126
    2      63
     2      3*21
       2     3   3*7
 this is somewhat of my factor tree
the answer is 2*3*3*7