How to solve this? I have no clue and also teach me on how to solve this! Thank you

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.

Assume that y varies inversely with x. if y=1.6 when x=0.5 find x when y=3.2

3x = 729 solve for x plz . it's urgent. will mark