Final answer:
The expression width_of_box % width_of_book != 0 checks if width_of_box is not divisible by width_of_book and evaluates to True if the remainder is not zero, indicating non-divisibility.
Step-by-step explanation:
An expression that evaluates to True if the integer associated with width_of_box is not divisible by the integer associated with width_of_book can be written using the modulus operator (%). The modulus operator gives the remainder of the division of two numbers. If width_of_box is not divisible by width_of_book, that means the remainder is not zero.
Therefore, the expression that checks for this condition would be width_of_box % width_of_book != 0. This expression will return True when the remainder is not zero, meaning the width_of_box is not completely divisible by the width_of_book.