40,43,40,39,50,23 what is the median?

How to do this , and can some one explain

Bring the fraction a/a-4 to a denominator of 16-a^2

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