so you have a total of 6 marbles, chance of picking a blue is 4/6 and then a red is 2/5, so multiply the 2 probabilities together to get 8/30 for part one.
second part is a little more tricky, you need to add up the combined probabilities of each event occuring. chance of getting blue marble first and then a red is 4/6 * 2/5, or 8/30 now add this to, the chance of getting a red and then blue which is 2/6 * 4/5= 8/30, add the 2 probabilities to get 16/30 as the probality of either occuring.
the third part is similar to the other parts. chance of getting 2 reds is 2/6 * 1/6 which equals 2/36 add to probability of getting 2 blues which is 4/6*3/5=12/30. now add 2/36 + 12/30 to get the total probablity