Answer:
By the Empirical Rule, 
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
The symbol of a standard deviation is
. So
When plotting sample statistics on a control chart, 99.7% of the sample statistic values are expected to fall within plus/minus how many sigma?
By the Empirical Rule, 
One of your friends gives you $10 for a charity walkathon -- this is your beginning amount.
Another friend gives you an amount per mile -- you will to calculate this value.
After 5 miles, you have raised $13.50 total --
-- Since one friend gave you $10.00, subtract this from the $13.50 to give you the amount by walking the 5 miles
-- $10.00 - $13.50 = $3.50
-- Since you walked 5 miles, divide $3.50 by 5 to give you $0.70 per mile earned.
So, an equation that represents the amount of money earned is: y = $0.70x+$10.00.
This is in slope-intercept form; the slope is $0.70 and represents the amount of money earned per mile and the intercept is $10.00 and represents the initial amount of money that you were given.