Hi,
27 coins.... CENTS make sense. Let s represent the amount of Quarters:
25x + 10(27-x) = 450¢
15x = 180
x = 12, number of Quarters. There are 15 Dimes
CHECKING our answer***
25*12 + 10*15 = 300¢ + 150¢ = 450¢ 0r $4.50
Wish You the Best in your Studies.