It would be 28-10=x because your ending up with 28 after earning 10 you would get that. Hope this works!
Answer:
Proportionality Constant = k = 
Step-by-step explanation:
Equation is:

=> 
Comparing it with
, where k is the proportionality constant, We get:
Proportionality Constant = k = 
I got 27.5 for the mean
mean: you add up all the #'s and divide them my their quantity( in other words by how many numbers there are)
In your case you have 8 numbers, you add them and divide them by 8!
Hope it helps ;)