What is the cost of operation of a central air conditioner that uses 3.5 kilowatts and runs for 12 hours a day for one week at a cost of 9.53 per kilowatt hour

Hiroaki wants to find 3 3/4 - 7/8 explain why he must rename 3 3/4 to do the subtraction.

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?

Can someone me out here number 4 plz