Samrud reads $$\frac{1}{3}$$ of a story book on the first day, $$\frac{1}{2}$$ of the remaining book on the second day and $$\frac{1}{4}$$ of the remaining book as on the end of the first day, on the third day, and is left with 23 pages unread. The number of pages of the book is

Take the whole book as 1. After the first day $$\frac{2}{3}$$ is left. On the second day he reads half of that, which is $$\frac{1}{3}$$ of the book, so $$\frac{1}{3}$$ of the book is still left. On the third day he reads $$\frac{1}{4}$$ of $$\frac{2}{3}$$, which is $$\frac{1}{6}$$ of the book. The unread part is $$\frac{1}{3} - \frac{1}{6} = \frac{1}{6}$$ of the book, and this equals 23 pages, so the book has $$6 \times 23 = 138$$ pages.