How much for each pencil and each binder

Question

3 pens and 6 binders cost $54.15

7 pens and 4 binders cost $54.85

Answer 1

3p + 6b = 54.15      {equation 1}

7p + 4b = 54.85      {equation 2}

 

To eliminate one variable, multiply equation 1

by 2 and equation 2 by -3 and add equations.

 

6p + 12b =   108.30

-21p- 12b = -164.55

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

-15p = -56.25

p = -56.25/(-15)

 

p = $3.75

 

Substitute that value for p into equation 1

and solve for b.

 

3(3.75) + 6b = 54.15

11.25 + 6b = 54.15

6b = 42.90

b = 42.90/6

b = $7.15

 

Pens cost $3.75

Binders cost $7.15