Perry observes the opposite, parralle walls of a room. in how many lines do the planes containing walls intersects

In a singing competition, there are 150 participants. at the end of each round, 40% of the participants are eliminated. how many participants are left after n rounds?

What is the name of a polygon that has four congruent sides and theses angle measures 60,120,60,120?

What is the point of inflection for the function f(x)=2cos4x on the interval (0, pi/2)