I am pretty sure the answer is 82.5 unrounded.
Answer: The expected waiting time is 
Step-by-step explanation:
Since we have given that
Average waiting time for slow elevator = 3 min
Average waiting time for fast elevator = 1 min
probability that a person choose the fast elevator = 
Probability that a person choose the slow elevator = 
So, the expected waiting time would be
![E[x]=\sum xp(x)=3\times \dfrac{1}{3}+1\times \dfrac{2}{3}\\\\=1+\dfrac{2}{3}\\\\=\dfrac{3+2}{3}\\\\=\dfrac{5}{3}\\\\=1\dfrac{2}{3}\ min](https://tex.z-dn.net/?f=E%5Bx%5D%3D%5Csum%20xp%28x%29%3D3%5Ctimes%20%5Cdfrac%7B1%7D%7B3%7D%2B1%5Ctimes%20%5Cdfrac%7B2%7D%7B3%7D%5C%5C%5C%5C%3D1%2B%5Cdfrac%7B2%7D%7B3%7D%5C%5C%5C%5C%3D%5Cdfrac%7B3%2B2%7D%7B3%7D%5C%5C%5C%5C%3D%5Cdfrac%7B5%7D%7B3%7D%5C%5C%5C%5C%3D1%5Cdfrac%7B2%7D%7B3%7D%5C%20min)
Hence, the expected waiting time is 
The answer you selected is correct
3x - 4y = 16
3x = 4y + 16
x = 4y/3 + 16/3
Answer:

Step-by-step explanation:
Let x be the number of minutes she can continue, since she's already 20 feet below the ocean surface and is diving at the rate of 20 ft/minute, her depth with respect to x would be
20 + 20x
But she doesn't want to reach more than 100 feet below the surface
