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