Question 171135
A coin collection consists of 14 coins with a value of $1.35. The coins are nickels, dimes, and quarters. The number of nickels is three less than twice the number of dimes. How many of each coin is there in the collection.
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Let x = number of dimes
then from "The number of nickels is three less than twice the number of dimes."
2x-3 = number of nickels
and from "A coin collection consists of 14 coins"
14-x-(2x-3) = number of quarters
17-3x = number of quarters
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Finally, because we know the total is $1.35
1.35 = .10x + .05(2x-3) + .25(17-3x)
1.35 = .10x + .10x - .15 + 4.25 - 0.75x
1.35 = 4.1 - 0.55x
-2.75 = - 0.55x
5 = x (number of dimes)
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number of nickels:
2x-3 = 2(5)-3 = 10-3 = 7 
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number of quarters:
17-3x = 17-3(5) = 17-15 = 2