Boxes that are 18 inches tall are being stacked next to boxes that are 24 inches tall. what is the shortest height at which the two stack will be the same height

Can someone me and do the problem plz so i can understand it more better

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?

:24% of students in a class are girls. if there are less than 30 students in this class, how many students are there? how many girls are there?