How do i find population standard deviation

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?

Labc is reflected across x = 1 and y = -3. what are the coordinates of the reflection image of a after both reflections?

Write the point-slope form of the line passing through (2, -12) and parallel to y=3x.