Multiply each payout by the corresponding probability and take the total:
E[X] = 0×0.5 + 5×0.2 + 8×0.15 + 10×0.1 + 15×0.05 = 3.95
ANSWER
The constant of variation is 6.
EXPLANATION
The inverse variation equation is:

We want to find the constant of variation, when x=-3 and y=-2.
We substitute the values for x and y to get,

Multiply out the left hand keeping in mind that negative times negative yields a positive result.
This implies that;

Hence the constant of variation is 6.
4 12 18
:) fun little riddle
You answer would be 27, if I did my maths correct.
You get 27 by doing:
9*4=36
36-9=27
Correct me if I am wrong thank you!