Andy scored 90 on the last history exam. he scored 81 this time. by what percent did his score decrease?

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?

Use sigma notation to represent the following series for 9 terms.

Given the following linear function sketch the graph of the function and find the domain and range. ƒ(x) = -5x + 4