Answer:
Step-by-step explanation:
The graph shows you the value stored on the card dropped by $14 when Gina rented 4 videos. Thus the cost of each one is ...
... $14/4 = $3.50
Gina now has $84 on the card, so can rent an additional ...
... $84/$3.50 = 24 . . . . videos
_____
Division is a way to do "repeated subtraction." That is, if we were to subtract $3.50 from $84 repeatedly, we would find we could do it 24 times.
Let 
denote the value on the 
-th drawn ball. We want to find the expectation of 
, which by linearity of expectation is
![E[S]=E\left[\displaystyle\sum_{i=1}^5B_i\right]=\sum_{i=1}^5E[B_i]](https://tex.z-dn.net/?f=E%5BS%5D%3DE%5Cleft%5B%5Cdisplaystyle%5Csum_%7Bi%3D1%7D%5E5B_i%5Cright%5D%3D%5Csum_%7Bi%3D1%7D%5E5E%5BB_i%5D)
(which is true regardless of whether the 
are independent!)
At any point, the value on any drawn ball is uniformly distributed between the integers from 1 to 10, so that each value has a 1/10 probability of getting drawn, i.e.
and so
![E[X_i]=\displaystyle\sum_{i=1}^{10}x\,P(X_i=x)=\frac1{10}\frac{10(10+1)}2=5.5](https://tex.z-dn.net/?f=E%5BX_i%5D%3D%5Cdisplaystyle%5Csum_%7Bi%3D1%7D%5E%7B10%7Dx%5C%2CP%28X_i%3Dx%29%3D%5Cfrac1%7B10%7D%5Cfrac%7B10%2810%2B1%29%7D2%3D5.5)
Then the expected value of the total is
![E[S]=5(5.5)=\boxed{27.5}](https://tex.z-dn.net/?f=E%5BS%5D%3D5%285.5%29%3D%5Cboxed%7B27.5%7D)
You would probably find it on the altitude or height.
So you will need to solve for x and y before evaluating 2x+y....
2x-y=9, y=2x-9 now this will make 4x^2-y^2=171 become:
4x^2-(2x-9)^2=171
4x^2-(4x^2-36x+81)=171
36x-81=171
36x=252
x=7, now we can use 2x-y=9 to solve for y...
2(7)-y=9
14-y=9
-y=-5
y=5
now we know that x=7 and y=5, 2x+y becomes:
2(7)+5
14+5
19
