Probability of Warcraft So I have this probability exercise from Khan Academy, which is about World of Warcraft ^^

Marvin lives in Stormwind city and works as an engineer in the city of
  Ironforge. In the morning, he has the choice to teleport, ride a
  dragon, or walk to work, and in the evening he has the same three
  choices for his trip home.
If Marvin randomly chooses his method of travel in the morning and in
  the evening, what is the probability that he teleports at least once?

It is easy to calculate the result if we write the possible outcomes and simply count which have at least one teleport, but thing is I can't be sitting and drawing stuff... So what I though of is that in 3 ways of transport then we have 3x3=9 possible outcomes, but I'm interested only in those that contain teleport, so I thought why don't remove teleport out of the equation so we have 2 ways of transport which gives us 4 possible outcomes, so now that we know this, from the 3 ways of transport (which is 9) we subtract the ones of 2 (which is 4) so we end up with 5 outcomes that we care about, namely the ones that contain teleport.. so we end up with 5/9... is that ideology correct?

It is correct, indeed. Sadly, i don't think you can apply the same logic to more complicated problems, or at least, not without having to do more calculations than if using other ways.
BTW, since there're no portals between Ironforge and Stormwind, shouldn't the answer be $0$? Or is he using mage portals? XD. Also, according to this: https://www.youtube.com/watch?v=CJ0fggxyBuA
it takes 1 hour 20 minutes to walk from IF to SW, and that is if he doesn't find any monster or dirty Horde on his way... have a nice trip, Marvin ;D
