X is U(0, 1), so the probability of less than 1/2 is 1/2.

And y is u (0,2), and the probability of less than 1/2 is 1/4.

So the probability that both of them are greater than 1/2 is (1-1/2) (1-1/4) = 3/8.

So we can get that at least one probability less than 1/2 is

p= 1-3/8=5/8