A maths problem for you to solve!

A snail has 1 foot, a person has 2 feet, a cat has 4 feet, an ant has 6 feet, and a spider has 8 feet. Using any combination of these creatures come up with different ways to make a total of: 12 feet 15 feet 20 feet You can use any creature more than once but you must use more than one type of creature. For example if I was trying to make 12 feet I could say that a cat, plus an ant, plus a person equals 12 feet because 4 + 6 + 2 = 12. I could record this on paper by writing 1 cat + 1 ant + 1 person = 12.