And equation that equals 23 that has a negative in it but the answer is positive

What is the ratio if counted 14 robins out of 150

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

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?