The standard deviation is about 3.81
To find standard deviation on calculator hit stat, 1, enter in each number, hit stat again, the hit the arrow to go to calc, then 1, and enter until it shows you the stats. The icon that says Sx is standard deviation for the data set you entered.
The slope is -10, I used a graph for this.
9514 1404 393
Answer:

Step-by-step explanation:
The left section is defined at x = -5, but not at x = 0, so the interval for that definition is -5 ≤ x < 0. The function value on that interval is constant: 3.
The right section is defined a x = 5, but not at x = 0, so the interval for that definition is 0 < x ≤ 5. That section is a straight line with a slope of -1 and a y-intercept of 1. The function value on that interval can be written -x+1.
Then the piecewise definition is ...
f(x) = {3, for -5 ≤ x < 0; -x+1, for 0 < x ≤ 5}
The price for each instructor will be the same at 3 hours. How I determined this answer:
First off, you need to add the initial price and hourly price for each person together, so you already know how much it will cost for 1 hour, including the initial fee. Here's how you do it:
Ieda: $11.00 (hourly price) + $8.50 (initial fee) = $19.50 (for 1 hour)
Thanh: $10.50 (hourly price) + $10.00 (initial fee) = $20.50 (for 1 hour)
Now that you have the price for 1 hour including the initial fee, now you need to find the price for each hour after that. Here's how I did that:
I created a graph that looked like this:
Hours: 1 2 3
Ieda: 19.50 30.50 41.50
Thanh: 20.50 31.00 41.50
Here's how I figured out the price for each hour:
Ieda:
Hour 1 (including initial price):
$11.00 + $8.50 = $19.50
Hour 2 (excluding initial price): Only add the hourly price after Hour 1!
$19.50 + $11.00 = $30.50
Hour 3 (excluding initial price):
$30.50 + $11.00 = $41.50
Thanh:
Hour 1 (including initial price):
$10.50 + $10.00 = $20.50
Hour 2 (excluding initial price):
$20.50 + $10.50 = $31.00
Hour 3 (excluding initial price):
$31.00 + $10.50 = $41.50
So, looking at the graph, their prices are the same once each instruction reaches 3 hours. ($41.50)
I hope I was able to help you! :)