Answer
The price per pencil is $0.17.
Work Step by Step
Lets represent price in total with "p" and the number of pencils you buy as "b." Now, lets create an equation that relates the two quantities as a direct variation:
p=bk (k is the price per pencil)
Now, substitute the information given to us in the question about one set of total price and number of pencils bought:
0.51=3k. (Divide both sides by 3)
0.17=k
So the price per pencil is $0.17.
