9.6 written as a fraction

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

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?

How do i put 3(x+7) in distributive property