Cho hình chóp S. ABCD có ABCD là hình thang cân, AD//BC, AD=2BC=8a. Góc ABC=120 độ.Gọi o là trung điểm AD. SO vuông góc mp ABCD. Diểm M là trung điểm của cạnh SA. H là hình chiếu của M lên mặt phẳng (SBO). Độ dài MH bằng?

How do you use the elimination method for this question? explain, because i really want to understand!

Abag contains 3 red marbles, 2 blue marbles, and 2 green marbles. one marble is picked, then another marble. assume that the selections are made with replacement. a) find the probability of picking two red marbles with replacement. b) find the probability of picking a red marble and a blue marble. assume the selections are made without replacement. c) find the probability of picking two red marbles without replacement. d) find the probability of picking a red marble and a blue marble without replacement.

Tatiana reads 40 pages of her book every night for x number of nights. write an expression that shows the number of pages she has read