Pg 314 (326) - Q18
This is a real confusing problem, but once you sort it out, it really isn't that tough. You've got the frogs(FR) is equal to one more than the number of cats(C); therefore, you've got FR=1+C. And it says the fish is three times the number of frogs. Well, if we said the frogs are equal to the cats plus 1, then the fish would be equal to three times the sum of cats plus 1. So, you'd have 3 cats plus 3, and you'd have the cats. The equation you are left with is C+C+3(which would represent the fish)+C+1(which would represent the frogs). Adding that up, you get 5X+4. The only one of these answer choices that you subtract 4 from that would leave you with a whole number for C(because you can't have half of a cat) would be E, 19(which would mean there are 3 cats.