Answer:
There are 6 dimes and 9 quarters.
Explanation:
Represent the number of dimes and the number of quarters by d and q.
Then d + q = 15, or q = 15 - d.
Also, ($0.25)q + ($0.10)d = $2.85, or 5q + 2d = 57.
Substituding 15 - d for q, we get 5(15 - d) + 2d = 57, or
75 - 5d + 2d = 57, or
75 - 3d = 57, or
3d = 18. Thus, there are 6 dimes. Since q = 15 - d, q = 15 - 6 = 9.
There are 6 dimes and 9 quarters.