Question

When Jeremy made 8 black and white copies and 2 color copies at a copy shop, the cost was $1.20. When he made 10 black and white copies and 10 color copies, the cost was $3.00. How much do black and white copies cost? ​

Answer 1

Answer:

10¢

Step-by-step explanation:

First, to be able to differentiate between the B&W and Color copies, use x in place of the B&W copies and y in place of the Color copies.

Then, write a system of equations to solve (the system of equations input was not working, so there is no brace):

 8x + 2y = $1.20

 10x + 10y = $3.00

Then, solve the system of equations:

   8x +  2y = $1.20

 10x + 10y = $3.00

Isolate x to be able to substitute:

8x + 2y = $1.20

8x = -2y + 1.2

x = -2/8y + 1.2/8

x = -0.25y + 0.15

Substitute:

10x + 10y = $3.00

10 (-0.25y + 0.15) + 10y = 3

-2.5y + 1.5 + 10y = 3

7.5y + 1.5 = 3

7.5y = 1.5

y = $0.20

Now that you have the cost of the Colored copies, you can plug it in to find the B&W copies:

8x + 2y = $1.20

8x + 2(0.2) = 1.2

8x + 0.4 = 1.2

8x = 0.8

x = $0.10