Question 951120
Let d = number of dimes. 
Then 10d = number of pennies, and d/2 = number of quarters. Let n = number of nickels. 


1(10d) + 10(d) + 25(d/2) + 5n = 2660 
10d + 10d + 12.5d + 5n = 2660 
32.5d + 5n = 2660 


Also, all types of coins added up = 742, so 
10d + n + d + d/2 = 742 
11.5d + n = 742 
n = 742 - 11.5d 


32.5d + 5(742-11.5d) = 2660 
32.5d + 3710 - 57.5d = 2660 
-25d = -1050 
d = 42 


42 dimes, 420 pennies, 21 quarters, which leave 
259 nickels.