Explanation:
Let f(x) be number of yellow pencils and x be number of blue pencils.
We have been given that Shawna found out there are 4 yellow pencils for every blue pencil. We can represent this information in an equation as:
Therefore, our desired equation will be:
.
Now let find number of yellow pencils for the given number of blue pencils by substituting the number of blue pencils in our equation as: