Two friends want to buy a snack. They combine their money and find they have $4.15, consisting of quarters, dimes, and nickels. If they have 37 coins and the number of quarters is half the number of nickels, how many quarters do they have? Choose the correct choice:
A) 9  B) 10  C) 11  D) 12  E) 13
Let x be the number of quarters. Then 2x is the number of nickels.   (1) 25x + 10x + 10D = 415. Then 7x + 2D = 83   (2) 3x + D = 37. Then 6x + 2D = 74   Let's subtract equation (2) from equation (1).   x = 9   The answer is 9.
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Two friends want to buy a snack. They combine their money and find they have $4.15, consisting of quarters, dimes, and nickels. If they have 37 coins and the number of quarters is half the number of nickels, how many quarters do they have?