The cumulative distribution function (CDF) F(x) defines the probability that a random variable X takes a value less than or equal to x. For F(30):

F(30) = P(X ≤ 30) = P(X = 10) + P(X = 20) + P(X = 30) = 10/100 + 20/100 + 30/100 = 60/100 = 0.6

Therefore, the CDF at X=30 is 0.6 or 60%.