P(3<=X) is exactly the same as P(X>=3) just FYI.Now what that means is that it's asking you for the probability that X is equal to or greater than 3. Now the table in the back tells you P(X<=x), so you need to change from P(X>=3) to make it X is less than something. The table tells you the combined probability of all the numbers leading up to and including x. If you think about the sum of all the probabilities, the answer is 1. So if P(X>=3)+P(X<=x)=1 and P(X>=3) includes all the values of 3 and up, what would x be to make P(X>=3)+P(X<=x) = 1