Question 534740
There were 12 female pups

First, what I did was write 1, 2, and 3 on a piece of paper. 
Then, I wrote numbers 1 through 6 around the number 1, because the first litter had 6 pups.
Then, I wrote numbers 1 through 5 around the numbers 2 and 3, because the second and third litters each had 5 pups.
Then I counted all the pups, from all 3 litters, and circled every fourth pup; meaning that pup was a boy
Then I counted all the uncircled numbers, which were all the female pups, which came out to be 12.