Can anyone pls say all the formulas in chapter number system class 9 ncert

Ben bowled 124 and 188 in his first two games. what must he bowl in his third game to have an average of at least 160?

Four airplanes carrying a total of 400 passengersarrive at the detroit airport. the airplanes carry, respectively,50, 80, 110, and 160 passengers. a) one of the 400 passengers is selected uniformly at random. let x denote the number of passengers that were on theairplane carrying the randomly selected passenger. find var(x)for x as given in the problemb) one of the 4 airplane drivers is also selected uniformly atrandom. let y denote the number of passengers on the chosen driver’s airplane. find var(y) for y as given in the problem

Simplify. (-2)^-3 a. -8 b. -1/8 c. 1/8 d. 8