Question 1187432
My piggy bank has 28 coins in it that are only nickels, dimes, and quarters.  I have $3.25 total.
The number of quarters is one less than the number of nickels.  
How many of each coin do I have?
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n + d + q = 28
5n + 10d + 25q = 325 ---> n + 2d + 5q = 65
q = n-1
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Sub for q
n + d + n-1 = 28
2n + d = 29
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n + 2d + 5q = 65
n + 2d + 5(n-1) = 65
6n + 2d = 70 ---> 3n + d = 35
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3n + d = 35
2n + d = 29
---------------------- Subtract
n = 6
q = 5
d = 17