Jenny recieved 6: 10 in tips one afternoon. all of her tips were in quarters, dimes, and nickels. there were five less dimes than quarters and seven less nickels than dimes. how many of each kind of coin was there.

1 nickel is 5c, 1 dime is 10 c, 1 quarter is 25 c. 
Let number of nickels be n. Seven less nickels than dimes, so, 
number of dimes is n + 7. Five less dimes than quarters, so, 
number of quarters is n + 12. 
Multiply number of each type by each value and total will be the tips received. 
5n + 10(n + 7) + 25(n + 12) = 40n + 370 = 610 
40n = 240 
Number of nickels was 6 and their value was 30 c 
Number of dimes was 13 and their value was 130 c 
Number of quarters was 18 and their value was 450 c

The correct answer is $90