Question

A collection of nickels, dimes, and quarters totals $8.20. The number of nickels and dimes
together is twice the number of quarters. The value of the nickels is one-third the value of the
dimes. How many of each kind of coin are in the collection?

Answer 1

You should build a system of equations to solve this.
Consider nickel = n, dime = d, quarter = q.
We know nickel = 5 cents, dime = 10 cents, quarter = 25 cents and $8.20 = 820 cents.
The first equation would be:
5n + 10d + 25q = 820
The second equation:
(n + d)*2 = q
The third equation:
n = 1/3d

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