When to use sample vs population standard deviation

Shryia read a 481 -page-long book cover to cover in a single session, at a constant rate. after reading for 1.5 hours, she had 403 pages left to read. how fast was shryia reading? pages per hour how long did it take her to read the entire book? hours plz i realy need this

Somone me i want to know what 18 hours out of 24 hours in a fraction

The vertex of this parabola is at (-2,-3). when the x-value is -1, the y-value is -5. what is the coefficient of the squared expression in the parabola's equation?