Write and solve four different word problems for 21 divided by 4

Find the sum to the equation 3+6+9+

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?

Astocks price gained 3% in april and 5% in may and then lost 4% in june and 1% in july during which month did the stocks price change the most