The answer relies on whether the balls are different or not.
If they are not, which is almost certainly what is intended.
If they are, the perceptive is a bit different. Your
expression gives the likelihood that a particular set of j balls
goes into the last urn and the other n−j balls into the other urns.
But there are (nj) different possible sets of j balls, and each of
them the same probability of being the last insides of the last urn, so the
total probability of completing up with exactly j balls in the last
urn is if the balls are different.
See attached file for the answer.
X = 360 - (122+58+58)
x = 360 - 238
x = 122
Answer:
11.34x + 9.45y = 141.75
y = (141.75 - 11.34x)/9.45
y = -1.2x + 15
Draw a straight line only in the first quadrant connecting these points:
(0,15)
(12.5,0)
Please put the image so I can see and help.
The length of the hypotenuse is 5.83 inches long so between 5 and 6 inches