Which equation can be used to solve the following word problem?

emilio has 6 more nickels than dimes, and the total value of his coins is $2.10. how many nickels does he have? let n represent the number of nickels.

a: 0.10(n-6)+0.05n=2.10
b:
0.10n+0.05(n+6)=2.10
c: 0.10n+0.05n+6=2.10
d:
0.10(n+6)+0.05n=2.10

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?