Answer:
Explanation:
Well the probabilities should all up to 1. This means pr(x<6) + pr(x=6) + pr(x>6) = 1.
So plugging in the known values we get:
To make things easier, let's multiply the 1/7 by 4/4 and 1/4 by 7/7
Now combine like terms:
Subtract 11/28 from both sides