Soja finished 2/3 of a book. She calculated that she finished 100 more pages than she has yet to read. How long is her book?  Options
A) 300  B) 150  C) 130  D) 90  E) 210

Rationale: let x be the total number of pages in the book , then she finished 2 / 3 * x pages . then she has x − 2 / 3 * x = 1 / 3 * x pages left . 2 / 3 * x − 1 / 3 * x = 100 1 / 3 * x = 100 x = 300 so the book is 300 pages long . answer is a .
Answer: A