How do you write 280.75 in expanded form

Given the following sampling distribution of one mean with a sample size 49, from a normally distributed population,find the population standard deviation, o.79828588912497

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. how many hours after the truck's departure will the two meet?

What is the distance between point a and b