Help! GHJ Café sells Medium and large coffees to locals in Downtown Dallas. If 7 medium cups and 10 large cups of coffee are sold, the café makes $68.75 in sales. If 10 medium and 15 large cups are sold, the total sales is $101.25. How much does a large cup of coffee sell for at GHJ Café?

Large cup cost $4.25

Step-by-step explanation:

Medium:  x

   Large:  y

Constraints:

  7x + 10y = 68.75

  10x + 15y = 101.25

Isolate y variable:

     (7x + 10y = 68.75) * -10    ===>    -70x - 100y =  -687.50

   (10x + 15y = 101.25) * 7       ===>     70x + 105y = 708.75

   add the two equations                                 5y = 21.25

   divide by 5                                                      y = 4.25

13

step-by-step explanation:

divide the cost of the total of sodas you bought by the cost of one soda, for example:

$24.57 divided by $1.89 is 13 which means you bought 13 sodas