Jillian is selling boxes of cookies to raise money for her basketball team. The 10 oz. box costs 3 point 5 0 dollars , while the 16 oz. box costs 5 point 0 0 dollars At the end of one week, she collected 97 point 5 0 dollars , selling a total of 24 boxes. The system of equations that models her sales is shown. x plus y is equal to 24; 3 point 5 0 x plus 5 point 0 0 y is equal to 97 point 5 0 Solve the system of equations. How many 10 oz. boxes were sold?
Let x be the number of 10 oz. boxes and y the number of 16 oz. boxes. From x + y = 24, x = 24 − y; substituting into the money equation gives 3.50(24 − y) + 5.00y = 97.50, so y = 9 and x = 15. Therefore, 15 10 oz. boxes were sold, which is choice C.
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