Help very confusing to me???!

Given f(x) = 17-x^2what is the average rate of change in f(x) over the interval [1, 5]?

Consider a cube that has sides of length l. now consider putting the largest sphere you can inside this cube without any point on the sphere lying outside of the cube. the volume ratio -volume of the sphere/ volume of the cube is 1. 5.2 × 10−1 2. 3.8 × 10−1 3. 1.9 4. 2.5 × 10−1 5. 3.8

:24% of students in a class are girls. if there are less than 30 students in this class, how many students are there? how many girls are there?