It sounds like you haven't learned anything very advanced, so for the first question they probably expect you to state either the mean or the median....
You can't just multiply two inequalities together, when negative numbers are possible. The fact that a >= 4 and b > -5 does not imply that ab > -20;...
These two sentences sound as if you want, in addition to the probability that all nine dice roll 1 to 15, the individual probabilities for exactly 1,...
I was a software engineer for many years, and have been teaching at a community college since 2004. Since 1998, I was a part of Ask Doctor Math (http://mathforum.org/dr.math/ and now http://themathdoctors.org/).