The left and right page numbers of an open book are two consecutive integers whose sum is 403. Find

The left and right page numbers of an open book are two consecutive integers whose sum is 403. Find these page numbers.

Page numbers left and right are consecutive integers. So we want to find a number n and n + 1 where:
n + n + 1 = 403

Combining like terms, we get:
2n + 1 = 403

Typing that equation into our search engine, we get:
n = 201

This is our left hand page. Our right hand page is:
201 + 1 = 202