Let the price the bookstore paid for the book be $x$.

The bookstore marks up the price by 25%, so the selling price can be expressed as: $x + 0.25x = 1.25x$

We are given that the selling price is $79. Therefore: $1.25x = 79$

To find $x$, divide both sides by 1.25: $x = \frac{79}{1.25}$

Calculating this: $x = 63.20$

So, the bookstore paid $63.20 for the book.

Would you like further explanation or have any questions?

Here are some related questions:

1. How would the calculation change if the markup was 30% instead of 25%?
2. If the bookstore had a sale with a 10% discount on the $79 selling price, what would be the new selling price?
3. What would the markup percentage need to be for the bookstore to sell the book at $100?
4. How can we calculate the original price if we know the markup percentage and final price?
5. How much profit does the bookstore make on each book sold at $79?

Tip: To reverse a percentage increase, divide the final price by $1 + \text{markup rate}$.