100 POINTS! I WILL MARK BRAINLIEST. ONLY ANSWER IF YOU KNOW HOW TO DO IT. RANDOM ANSWERS WILL BE REPORTED! :)

How do you solve a question like this?

65% of students in your school participate in at least one after school activity. if there are 980 students in you school, how many do not participate in an after school activity?

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)