Question

On Monday Harold picked up 6 donuts and two large coffees for the office. He paid $5.20. On Tuesday Melinda picked up four donuts and five large coffees for the office. She paid $6.95. What is the cost for one donut? What is the cost for one large coffee?

Answer 1

We will start solving as follows:

*First: We write the equations described in the problem, those are:

Monday:

`6d+2c=5.20`

Tuesday:

`4d+5c=6.95`

*Seciond: We operate the expressions in order to eliminate one of the variables and solve for only one of them, that is:

5 (6d + 2c = 5.20)

-2 (4d + 5c = 6.95)

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

30d + 10c = 26

-8d - 10c = -13.9

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

22d = 12.1 => d = 0.55

Now, we have the price for each donut is $0.55. So, in order to determine now the value of the coffee we input this value in one of the original equations and solve for c, that is:

`4(0.55)+5c=6.95\Rightarrow2.2+5c=6.95`
`\Rightarrow5c=4.75\Rightarrow c=0.95`

So, the value for each coffee is $0.95.