Question 992760
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Let D = the number of dimes. Then
The value of the dimes = 0.10D
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I have...six less quarters than dimes 
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The number of the quarters = D-6
Value of quarters = 0.25(D-6)
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and ten more than seven times as many nickles than dimes
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number of nickels = 7D+10
Value of nickels = 0.05(7D+10)

coins totaling $13.00

Value of dimes + Value of quarters + value of nickels = 13.00
       D       +      0.25(D-6)    +    0.05(7D+10)   = 13.00

Multiply through by 100 to clear decimals:

  100D + 25(D-6) + 5(7D+10) = 1300

100D + 25D - 150 + 37D + 50 = 1300 

That works out to 8 3/4 dimes, so something is wrong 

Edwin</pre>