What is the page number for,"There must be something in books, things we can't imagine, to make a woman stay in a burning house; there must be...

The quote you refer to is from Ray Bradbury's novel,
Fahrenheit 451.

This part of the story
is a turning point for Guy Montag, one of the firemen who is responsible for burning
houses where books are hidden. Montag is already having some serious doubts about books,
primarily because of questions from his neighbor Clarissa who shakes up his world by
asking him about things no one else thinks to ask. This is not surprising in that the
society at large would rather have its members "intellectually
anesthetized."

However, in this part of the book, the
firemen go to burn down the house of an old woman. As they throw books out the windows
and spray everything with kerosene—flamethrowers in hand—the woman refuses their
attempts to convince her to leave her home and her books. (Montag says this is unusual
because most of the time the houses they burn are already emptied of people.) In this
case, the woman does more than refuse to leave. Very carefully—almost casually—she takes
out a single match. Before the firemen can do anything, she lights the match to the
kerosene, setting not only her home, but also herself, on fire. This greatly shakes up
Montag, and it gives him a great deal to think about in terms of his own life: his job,
his existence at home, and what he wants for his future.

I
am not sure what edition of the novel you have. In my edition (which is dated), this
scene begins on page thirty-five. It is in "The Hearth and the Salamander" section (the
first section), a little more than half way to the second
part.