Find value of x. Cos y = 8/13

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 percent of 18 is 24? and plz explain thx.

Solve the following: 12(x^2–x–1)+13(x^2–x–1)=25(x^2–x–1) 364x–64x=300x