When solving a system of equations, how do you determine which method to use? (substitution, elimination, graphing)

Acharity is conducting a raffle, and it sells one ticket each to 35 women and 21 men. if 5 winners are randomly selected, what is the probability that they are all men? round to five decimal places. 0.00533 0.06268 0.09537 0.07776

Really need on these. i have no idea what to do

An advertising firm has an old computer that can prepare a whole mailing in 6 hours. with the of newer model the job is complete in 2 hours. how long would it take the newer model to do the job alone?