Question

Explain why multiplying by 6 is like multiplying by 3

Answer 1

3 is a factor of six, usually if there is something divisible by 6 it can be divided by 3

Answer 2

Since the prime factorization of 6 is 2*3, you can simply multiply by 3 and then multiply your answer by 2.
Example:
6*3=18
6*6= 6*3*2=36

Hope this helped!