I need help with this question but keep f getting decimals, it's not supposed to be a decimal for the answer. were solving systems by substitution

here's the question and will give brainy to someone who solves both

4x - 7y = 10
y = x - 7

x = 16 - 4y
3x + 4y = 8

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?

What does independent variable and dependent variable mean in math?

Mrs.sling bought a pound of green beans for $1.80. how much will mrs.tennison pay for 3 1/2 pounds of green beans?