Question 677885
the library started with an unknown {{{ x }}} number of books
The cash donation allowed them to double that number, so
then they had {{{ 2x }}} books
Then a book collector gave the library 4028 books, so then
they had {{{ 2x + 4028 }}} books
The total after that was {{{ 51514 }}} books, so
{{{ 2x + 4028 = 51514 }}}
{{{ 2x = 51514 - 4028 }}}
{{{ 2x = 47486 }}}
{{{ x = 23743 }}}
The library started with 23,743 books