Question

How many different ways can u make change for 75 cents using quarters, nickels and dimes?

Answer 1

I will give you some examples
7 dimes, one Nickel
6 dimes, three nickels
You take it from here.

Answer 2

Change OF 75 cents or change from a dollar (25 cents)?

In either case, I suggest you make a list instead of trying to derive a formula, or plugging into one we derive for you.

When you start making the list, perhaps a formula to use will become obvious.