Help me please this is really confusing and can you also put the step to step explanation thanks

He concluded that a heavier object dropped from the same height as a lighter object will land

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?

What does independent variable and dependent variable mean in math?