21,19,17,15 find next three\

Which of the fallowing best completes the sequence 5,10,15, a) 30 b) 22 c)25 d)35

The sum of two numbers is 86, and their difference is 20. find the two numbers

2people are trying different phones to see which one has the better talk time. chatlong has an average of 18 hours with a standard deviation of 2 hours and talk-a-lot has an average of 20 hours with a standard deviation of 3. the two people who tested their phones both got 20 hours of use on their phones. for the z-scores i got 1 for the chatlong company and 0 for talk-a-lot. what is the percentile for each z-score?