Question 1110679
WITHOUT A SYSTEM OF EQUATIONS:
Let us open the book at the place where the missing pages were torn off.
Assuming it is an American book (not a Japanese Manga novel),
and you are holding the book as if you were going to read it,
on the left side we see page number {{{x}}} .
{{{x}}}= the number on the last not torn page.
Facing that page, on the right side you have page number {{{2x+11}}} ,
"11 more than twice the number on their other facing page."
 
The difference of the page numbers is
{{{(2x+11)-x=23}}} .
That equation simplifies to {{{x+11=23}}} ,
and then to
{{{x=23-11}}} and {{{x=12}}} .
That is good, because when I open an American book,
the page on the left always has an even number.
 
The page facing page {{{12}}} has a number that is {{{23}}} more.
That number is {{{12+23=35}}} .
 
Pages {{{35}}} and up are still in the book.
Pages 1 through {{{35-1=34}}} were in the book originally,
but of those pages, only pages 1 through {{{12}}} are still in the book.
The difference is the
{{{34-12=22}}} pages missing.
 
Each sheet has two pages, one on each side, so those {{{22}}} pages
are in the {{{22/2=highlight(11)}}} sheets that were torn out of the book.