Final answer:
The book's price increased by $4, as calculated by subtracting the original price of $16 from the new price of $20.
Step-by-step explanation:
The student is asking how much the book's price increased from one week to the next.
To find out the increase in price, we subtract the original price from the new price.
The equation for this situation is p = 20 - 16, where 'p' represents the price increase.
To solve it, we subtract 16 from 20, which gives us p = 4. Therefore, the book’s price increased by $4.