Which equations support the fact that rational numbers are closed under addition? Select each correct answer.
+0.5 = 1
3/16 +3/16 = 6/16
35+ 5 = 415
V10 + (-V10) = 0

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?