Caleb is reading a book that is 90 pages long. He read 4/5 of the book on Sunday and 1/2 of the remainder on Tuesday. How many pages did Caleb have left to read?

He read 4/5 so there is 1/5 remaining 1/5 * 90 = 18 read half of this , then half of this remains = 9 pages left to read