PLZ PLZ help asap due in 10 minutes idk the answers plz help!!!

How do you determine whether a relationship represented as as graph is linear or nonlinear

You were told that the amount of time lapsed between consecutive trades on the new york stock exchange followed a normal distribution with a mean of 15 seconds. you were also told that the probability that the time lapsed between two consecutive trades to fall between 16 to 17 seconds was 13%. the probability that the time lapsed between two consecutive trades would fall below 13 seconds was 7%. what is the probability that the time lapsed between two consecutive trades will be between 14 and 15 seconds?

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)