I have 30 coins consisting of nickels and quarters. The total value of the coins is $4.10. How many of each kind do I have?

n + q = 30
n(0.05) + q(0.25) = 4.10
17(0.05) + 13(0.25)
17 + 13 = 30
0.85 + 3.25 = 4.10
You have 17 nickels and 13 quarters.