http://i54.tinypic.com/25qq81u.jpg
As in the diagram, for the first pick it can either be red or blue. For the second pick it can either be red or blue, and the same for the third.
Now, for working out the fraction of probablity, simply look at the number of favoured outcomes and divide it by the total number in the sample space.
In the first pick, the probablity of picking a red raffle is 100/200 = 1/2 and the probability of picking a blue raffle is the same. On the other hand, AFTER having picked a red raffle, the probablity of picking another red raffle is 99/199 (Because a red raffle has been picked out, and 199 total raffles remain)
Use similar logic to work out each fraction.
Hope that helps!