Hi,
28 quarters, nickels, and dimes, $3.15 total 0r 315¢
and three times as many dimes as quarters.
Let x represent the number of quarters and 3x the number of dimes
25x + 10(3x) + 5(28-4x) = 315¢
35x = 175
x = 5
5 Quarters, 15 Dimes and 8 Nickels
CHECKING our Answer***
125¢ + 150¢ +40¢ = 315¢ or $3.15