You don't need to list them. You can think through them. If you don't use any quarters, you can use from 0 through 6 dimes and the rest, if any, in nickels. That's 7 ways. If you use 1 quarter you can make the remaining 35 cents by using from 0 through 3 dimes and the rest in nickels. That's 4 ways. If you use 2 quarters you can make the remaining 10 cents with either 1 dime or 2 nickels. That's 2 ways. Answer 7+4+2 = 13 ways. Edwin