Question

Megan went to the store and bought 4 notebooks and 9 pencils for a total of $8.25. Joanne went to the same store and bought 7 notebooks and 14 pencils for a total of $14. What was the price per pencil and the price per notebook?

Answer 1

Let notebooks be x and let pencils be y

4x+9y=8.25 (equation 1)
7x+14y=14.00 (equation 2)

Multiply equation 1 by 7
So that you get 28x+63y=57.75

Multiply equation 2 by 4
So that you get 28x+56y=56.00

28x+63y=57.75 -
28x+56y=56.00
-----------------------
7y=1.75

Divide both sides by 7
1.75/7 is 0.25

So, now we know that one pencil costs 0.25 cents

Sub this y value into equation one

4x+9(0.25)=8.25

4x+2.25=8.25

Move 2.25 to the other side as a negative number

4x= 6

Divide both sides by 4

6/4 is $1.50

So, one pencil is equal to 0.25 cents and one notebook is equal to $1.50