Tim is reading a book. on monday he reads 3 pages. on each day after that, he reads 3 times the number of pages that he read on the previous day. how many pages does he read on thursday?

To solve this, let's make a "chart"

Monday : 3 pages
Tuesday : 3 x 3 = 9 pages
Wednesday : 9 x 3 = 27 pages
Thursday : 27 x 3 = 81 pages

Alternatively, you can say 3^4 (since we are dealing with 4 days), and that would also equal 81 pages

Therefore, he reads 81 pages on Thursday.