Let N be the number of nickels. Then the number of dimes is (30-N). Amount of money (cents) in nickels is 5*N. Amount of money (cents) in dimes is 10*(30-N). The condition says 5N = 2*(10*(30-N)). It is your equation to solve. Simplify and find N: 5N = 20*(30-N) ====> 5N = 600 - 20N ====> 5N + 20N = 600 ====> 25N = 600 ====> N == 24. Answer. 24 nickels and 6 = 30-24 dimes. Check Amount in nickels = 5*24 = 120 cents. Amount in dimes = 10*6 = 60 cents. ! Correct !.