"Fairy tale" has 100 pages, I have read 80 pages. (1) what percentage of the book has been read? (2) what percentage of the book is left

"Fairy tale" has 100 pages, I have read 80 pages. (1) what percentage of the book has been read? (2) what percentage of the book is left

(1)80/100=80%
(2)1-80%=20%