Answer:
...If Amy has 15 for a total of $2.70 and the coins are quarters and dimes, how many of each coin does she have?
x= coins of $0.25
(15-x)= coins of $0.10
0.25x+0.10(15-x)=2.7
0.25x+1.5-0.10x=2.7
0.15x=2.7-1.5
x= 1.2/0.15=8
we calculate the coins of $0.10=
15-8=7
she has 8 coins of $0.25, 7 coins of $0.10