Answer:
10/10
Step-by-step explanation:
<h3><u>MEAN</u></h3>
Mean is the average. To find the mean of a data set, you have to add all the numbers and divide the sum by the amount of numbers you added.
<em>In this equation, you have 8 numbers. That means you will be dividing by 8. </em>
The first thing you need to do is add all the numbers. Add:

Now that you have added all the numbers and got the sum, divide by 8. Remember that you will be dividing by 8 since you added 8 numbers.
Divide:

The mean is 66
<em>If you have any questions, feel free to ask in the comments! :)</em>
15 - 2(- 13s + 3) = 9s - 9 + 16s
15 + 26s - 6 = 25s - 9
9 + 26s = 25s - 9
26s - 25s = -9 - 9
s = - 18