Hello. I did a quiz and I do not know how to solve these questions as the picture below. Please explain them in detail. I want to know how to get the answer.
Thank you.

Solve 2x+y=3 x+y=5 in substitution method

The volume of a sphere is increased by 6%. calculate the corresponding percentage increased in it area.

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?