Which property of real numbers is shown below?

3 + ((-5) + 6) = (3 + (-5)) + 6

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?

What is x3+3x2−16x−48 divided by x−1?

What is the similarity ratio of a cube with volume 729m^3 to a cube with volume 3375 m^3