Carl has two more flips, and we want to know the probability that one and only one of those times it will be jelly side up. Assuming the basic heads/tails 50% probability each flip we have four possible outcomes: P P. P J, J P, J J, (btw P = plain side and J = Jelly side) and two of the four give us the one P wanted, so 2/4 = 50% probability.
Carl has a piece of toast that has jelly on one side, and he dropped it twice. both times, it landed with the jelly side up. if he drops it two more times, what is the probability that it will have landed jelly side up a total of three times? one over four one over three one over two two over three