y = mx , where m is a slope,
m= rise/run
We have y = 15x, so m =15 and rise/run =15, then
rise = 15, run = 1
Is there a photo? I know the last option is true but I feel like there should be a photo with this
The plot of the PDF shows the distribution is symmetric. This means that the mean is the same as the median, and that the 50% of the distribution lies to other side of this mean, i.e.
For this distribution, 
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14/99
Select 1 marble; the chance that it is white is 4/12. Select a 2nd marble; the chance that it is white is 3/11. Select a 3rd; the chance it is white is 2/10. Select a 4th; the chance it is red is 8/9. Select a 5th; the chance it is red is 7/8. The chance of getting this specific set of 5 marbles in this order is (4/12)×(3/11)×(2/10)×(8/9)×(7/8)=(2×7)/(11×10×9).
This specific set could occur in the permutation of 5 things taken 5 at a time where 3 are identical (white), and the other 2 are also identical (red). The formula for this is 5!/(3!2!)=10.
Combining the chance of getting white, white, white, red, red with the number of ways 3 white and 2 red could have been distributed in the draw of 5 marbles gives the answer:
{(2×7)/(11×10×9)}×10=14/99
A similar process will show that the chance of getting 5 red marbles is 7/99; 4 white and 1 red is 1/99; 2 white and 3 red is 42/99; and 1 white and 4 red is 35/99.
