NEED HELP NOW PLEASEEE, what algebraic expression must be added to the sum of 3x^2+4x+8 and 2x^2-6x+to give 9x^2-2x-5

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 long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

Hundred and tens tables to make 430 in five different ways