Ok, you multiply 3636 by 3, because you read that many pages for the first 3 days. you do the same for 4444.
36363=10,908
44443=13,332
Then you add.
10,908+13,332=24,240
Then you add 1010.
24,240+1010=25,250
There were 25,250 pages in the book. Hope it helps!