Tammy wants to get change for 30 cents. The only coins she can get are quarters, nickels, and dimes. How many different ways can she get 30 cents using only these coins?

Answer 1

qn
ddd
now replace each d with nn for the others.

Answer 2

Just list them:

Q D N
1 0 1
0 3 0
0 2 2
0 1 4
0 0 6