jillian is selling boxes of cookies to raise money for her basketball team. the 10 oz. box costs $3.50, while the 16 oz. box costs $5.00. at the end of one week, she collected $97.50, selling a total of 24 boxes. the system of equations that models her sales is below.

  x+  y= 24

3.50x  + 5.00y  = 97.50

solve the system of equations. how many 10 oz. boxes were sold?