Of the 320 students in 8th grade, 3/8 have a pet. how many students in 8th grade have a pet?

Can someone explain the elimination method to me for this problem?

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 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)

Qrst is a parallelogram. determine the measure of ∠q pls