The probability of rain is 2/5, what is the complementary event and its probability?

The complimentary event is the probability of it not raining. The probability of that is 1-2/5 = 3/5.

You cannot tell which number is greater because you don't know how many numbers follow after 8 or 3. It all depends on how many numbers follow afterwards.
Example: 
It could be 800 or 80,000
It could be 30,000 or 300,000

~ I hope you get what I mean. If you have any more questions, I'd be happy to help!