Can someone help me with this ladder method please

Question

Pete has 6 blue marbles and 15 white ones that he wants to divide into equal sets so he can use them as pieces for games they’ve created for their Kindergarten book buddies . He wants the same amount of blue marbles and the same amount of white marbles in each set. What is the greatest number of sets he can make?

Answer 1

Determine the greatest common factor, GCF:

6: 2, 3

15: 3, 5

The GCF is 3. Peter can make 3 groups with 2 blue and 5 white in each