Can somebody help with this please.

Which of the following is the missing term, a2, of the geometric sequence in which a1=2 and a3=200

Prove that 16^4-2^13-4^5 is divisible by 11.

F. a fair coin is thrown in the air four times. if the coin lands with the head up on the first three tosses, what is the probability that the coin will land with the head up on the fourth toss? a. 0 b. 1/16 c. 1/8 d. 1/2