Question 1204453
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Probably a formal algebraic solution, like the one shown by tutor @ikleyn, was wanted.  But you can get good mental exercise solving the problem informally, using logical reasoning and mental arithmetic.<br>
The number of nickels is 3 more than the number of dimes, and the total value is $3.60.<br>
Set aside those 3 "extra" nickels, worth $0.15, leaving a value of $3.45 for the remaining coins.<br>
Those remaining coins are equal numbers of nickels and dimes.  The value of one nickel and one dime is $0.15. $3.45/$0.15 = 23, so the remaining coins are 23 nickels and 23 dimes.<br>
Now add back in the other 3 nickels, making 26 nickels and 23 dimes.<br>
ANSWER: 26 nickels and 23 dimes<br>