Question

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?

Answer 1

Large cup cost $4.25

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

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add the two equations 5y = 21.25

divide by 5 y = 4.25