If a parking meter has 100 coins in it that add up to $14.50, how man are dimes and how many are quarters?
D + Q = 100
10D + 25Q = 1450
10(100 -Q) + 25Q = 1450
1000 -10Q + 25Q = 1450
15Q = 450
Q = 30 is the number of quarters
D = 70 is the number of dimes