What is the price of the coffee, doughnuts, and juice?

Question

Anne, Barry, and Cathy carpool together and frequently stop to get breakfast for themselves at a cafe. Anne orders 2 coffees, 2 juice, 2 doughnuts and pays 8 dollars. Barry orders 1 coffee and 3 doughnuts and pays $3.75. Cathy orders three coffees, 1 juice, and 4 doughnuts and pays $9.25

Answer 1

Anne: 2c + 2j + 2d = 8.00

Barry: c +         3d = 3.75

Cathy:3c +  j  + 4d = 9.25

 

You have 3 equations and 3 variables.  Multiply Cathy's equation by -2 and add it to Anne's.  This gives you an equation with just c and d in it.  Combine this with Barry's equation and you can find c, then d.  Once these are known, you can substitute them in Cathy's equation and find j.

 

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