a4 is wrong. How many education majors did they list?
b1 is wrong. What's the probability of picking a man with one pick (how many men are there? how many people are there)? Now that you've removed one man from the general population, what is the probability of picking another man (hint: the numbers used to calculate the probability for the first man have changed)? Now that you have two probabilities, what do you do with them? Hint: You want a man AND a man. See earlier post about and/or.
b2 is wrong. This is a little trickier. Just using probability, what you want is P(selecting a bio then a ling) OR P(selecting a ling then a bio)
Using combinatorics (counting techniques), you want the number of bio/ling pairs divided by the total number of pairs. That would be (50*25) / C(200,2) where C(200,2) means the number of combinations of 200 items selected 2 at a time.