State whether each situation involves a permutation or a combination.
a. choosing a class president, vice president, and secretary.
b. four tennis players from a group of nine.
c. eight toppings for ice cream

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. how many hours after the truck's departure will the two meet?

Is it greater than or less than7*3_9*2

As voters exit the polls, you ask a representative random sample of voters if they voted for a proposition. if the true percentage of voters who vote for the proposition is 63%, what is the probability that, in your sample, exactly 5 do not voted for the proposition before 2 voted for the proposition? the probability is