On August 5th, Joe started reading a 280-page book. He read an average of 15 pages each day. By the end of August 12th, what fraction of the pages was left unread (in simplest form)?

/ of the pages

From August 5th to August 12th, there are 8 days.

Therefore, Joe read 15 × 8 = 120 pages.

The pages unread: 280 – 120 = 160 pages

Therefore, of the pages were left unread.