Need because i never understand these kind of questions so don't just give me the answer but explain how you got the answer

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a. m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?

Alex took his brother to a birthday party. the party was scheduled to last for 1 and 3/4 hours but they stayed for 4/5 of an hour more. how long did she stay at the party?

Harry is at the depot in dover and has deliveries to make in edinburgh, glasgow and aberdeen. from dover which of the deliveries is the shortest distance?