Question

Twelve books cost $59.88 and

Answer 1

Answer:

Yes there is, and it is 4.99.

Step-by-step explanation:

The constant of proportionality (let's call it $\alpha$) will relate the number of books bought $N$ and their cost  $C$ in the following way:

$C={\alpha}N$

$\therefore \alpha =\frac{C}{N}$

For the 12 books:

$\alpha =\frac{59.88}{12} = 4.99.$

And for the 21 books:

$\alpha =\frac{104.79}{21} = 4.99.$

The $\alpha$ for the two purchases is the same, thus there is a constant of proportionality between the two purchases.

P.S: $\alpha$ is the price per book.