A). What is the probability of six tails out of nine tosses of a fair coin? The answer is 21/128. Please explain.

B). A donut shop bakes a dozen donuts at a cost of $4. To achieve a 33% profit on sales, what is the minimum sale price the donut shop should set each donut? The answer is 50 cents.

C). A candy store mixes jaw breakers worth 36 cents a pound with lolly pops worth 52 cents a pound to make a 200 pound mixture worth 40 cents a pound. How may pounds of lolly pop did the store use? The answer is 50 pounds.

I would appreciate it if you could explain the answers to me. Thanks.