Question 998032
n = number of nickels
d = number of dimes


5n + 10d = 515
n = d + 7


Substitute n = d + 7.


5(d + 7) + 10d = 515
5d + 35 + 10d = 515
15d = 480
d = 32


There are 32 dimes and 39 nickels.