I need help with math?!!?

Snowball has read 85 percent of a book which amounts to 238 pages. How long is the book?... ALSO another problem.. Molly's dinner with her family amounted to $125. She left $21.25 for a tip. What percent did she tip? ... I rly need help.. I need the answer.. but i also need to know HOW YOU DID IT! .. plz help.. thanks.. Im rly bad at math.. ahaha