Mark has $4.40 nickels and dimes.he has thirteen more nickels than dimes. How many of each does he have?
count the coins: n = d+13
count the value: 5n+10d = 440
5(d+13)+10d = 440
5d+65+10d = 440
15d = 375
d = 25
So, there are 25 dimes and 38 nickels