how much does one donut and one cup of coffee cost

Question

On Monday, Harold picked up four donuts and two large coffees for the office staff. He paid $4.66. On Tuesday, Melinda picked up five donuts and five large coffees for the office staff. She paid $8.00. What is the cost of one donut? What is the cost of one large coffee?

Answer 1

Let d = cost of donut

Let c = cost of large coffee

 

4d + 2c = 4.66    {equation 1}

5d + 5c = 8         {equation 2}

 

Let's solve be elimination. 

Multiply equation 1 through by 5

Multiply equation 2 through by -2

Add the equations and solve for d

 

20d + 10c = 23.3

-10d-10c = -16

--------------------

10d = 7.3

d = $0.73 for a donut

 

Substitute the value of d into one of the original equations

to solve for c

 

5(0.73) + 5c = 8

 

Finish from here to find the cost of a large coffee