The sum of page numbers on the facing pages of a book is 81. What are the page numbers?
The page numbers on facing pages of a book will always be consecutive. Therefore, let the left-hand page be denoted by x. Then the right-hand page would be x+1.
x+(x+1) = 81
2x + 1 = 81
2x = 80
x = 40.
So, the left-hand page has number 40, and the right-hand page has number 41.