Please help asap its very important

Which expression calculates the speed in meters per second of an object that travels a distance of 100 m every 20 seconds

Rachel reads 1/5 of the pages of a book plus 12 pages on the first day. on the second day, she reads 1/4 of the remaining pages plus 15 pages. on the third day, she reads 1/3 of the remaining pages plus 18 pages. on the fourth day, she reads the remaining 70 pages. how many total pages are in the book?

What is the difference between the predicted value and the actual value