Amy has ridden 28 miles of a bike course. The course is 40 miles long. What percentage of the course has Amy ridden so far?

Explain the answer and how to do it

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?

If 3x+8=3x+8 is it one solution or no solution