15. Susan read 72 pages of a storybook in the afternoon. She read $$ \frac{2}{5} $$ of the remaining number of pages of the storybook in the evening. She then found out that she still had $$ \frac{1}{3} $$ of the storybook to read. How many pages were there in the storybook?

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Let the total number of pages be $$ N $$.

1. After reading 72 pages in the afternoon, the remaining pages are:
   $$
   N - 72
   $$

2. In the evening, Susan read $$ \frac{2}{5} $$ of these remaining pages, so she read:
   $$
   \frac{2}{5}(N - 72)
   $$

3. The number of pages still left after the evening reading is:
   $$
   \text{Remaining pages} = \left(N - 72\right) - \frac{2}{5}(N - 72)
   $$
   Factor out $$ N - 72 $$:
   $$
   \text{Remaining pages} = \left(1 - \frac{2}{5}\right)(N - 72) = \frac{3}{5}(N - 72)
   $$

4. We are told that these remaining pages constitute $$ \frac{1}{3} $$ of the entire storybook, so:
   $$
   \frac{3}{5}(N - 72) = \frac{1}{3}N
   $$

5. To solve for $$ N $$, multiply both sides of the equation by 15 (the least common multiple of 5 and 3) to eliminate the fractions:
   $$
   15 \times \frac{3}{5}(N - 72) = 15 \times \frac{1}{3}N
   $$
   Simplify each side:
   $$
   9(N - 72) = 5N
   $$

6. Distribute and solve for $$ N $$:
   $$
   9N - 9 \times 72 = 5N
   $$
   $$
   9N - 648 = 5N
   $$
   Subtract $$ 5N $$ from both sides:
   $$
   4N - 648 = 0
   $$
   $$
   4N = 648
   $$
   $$
   N = \frac{648}{4} = 162
   $$

Thus, the total number of pages in the storybook is $$ 162 $$.
The storybook has 162 pages.

Susan read 72 pages of a storybook in the afternoon. She read of the
remaining number of pages of the storybook in the evening.
She then found out that she still had of the storybook to read.
How many pages were there in the storybook?

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Susan read 72 pages of a storybook in the afternoon. She read of the remaining number of pages of the storybook in the evening. She then found out that she still had of the storybook to read. How many pages were there in the storybook?