Question 893669
Difficult to explain here, but you build a tree diagram.  Start with the dimes, and work to progressively lower coin values.


0 dimes; how many ways can you choose nickels; for each of them how many ways can you choose pennies.


1 dime;  how many ways to choose nickels; for each of them how many ways to choose pennies.


2 dimes;  same set of questions.


3 dimes;   This combination itself already makes $0.30.


Count all of the combinations.