How many Hamilton Circuits are in K13?

Ineed with number 17 i don’t get it at alll

How many terms does the polynomial x^2 y^2 have

Monitors manufactured by tsi electronics have life spans that have a normal distribution with a standard deviation of 1800 hours and a mean life span of 20,000 hours. if a monitor is selected at random, find the probability that the life span of the monitor will be more than 17,659 hours. round your answer to four decimal places.