Sally reads 10 pages of a book on weekdays and 20 pages on weekends. If it takes 2 weeks for Sally to finish her book, how many pages that book has?
Let's think step by step below.
180
Two weeks has 5 * 2 = 10 weekdays.

Two weeks has 2 * 2 = 4 weekends.

On weekdays, she reads 10 * 10 = 100 pages in total.

On weekends, she reads 20 * 4 = 80 pages in total.

So the book has 100 + 80 = 180 pages.

.

Therefore, the answer is 180