Hi Dan. Use variables (letters) to represent the unknown quantities: d for dimes, n for nickels, and q for quarters.

"Helen has twice as many dimes as nickels".

So d = 2n.

"She has 5 more quarters than nickels".

So q = n + 5.

"She has $4.75".

So 0.25q + 0.10d + 0.05n = 4.75.

Now you have a system of three equations and three unknowns. Use the substitution method and/or the elimination method for simultaneous equations to reduce it to a single equation involving a single variable. Then solve for that variable and use its value to determine the other two variable quantities.

If you want some examples of using the "substitution method" or the "elimination method", just search for those terms in our Quick Search.

Cheers,
Stephen La Rocque.