We know that bitcoin is strong and all the wallets have milletry grade security but one of my stupid friend today said that maybe someone can hack it with just a calculater because with math and correct formulas we can even predict gambling bets if that is possible then maybe there is any chance of this
I have encountered my fair share of these type of people around me and in my experience the best answer to these people is "yes, you are right"!
just let them stay in their dream world dreaming about hacking and their
super advanced mathematical formulas I bet your friend has to think for 10 minutes to come up with the result of 2+2

I personally don't allow myself to give opinion on the matter, not unless I am fully aware of the range of ECDSA private keys, the secp256k1 elliptic curve and some other stuff regarding creating a private key
maybe you should introduce your friend to google and teach him how to search:
http://bitcoin.stackexchange.com/questions/2847/how-long-would-it-take-a-large-computer-to-crack-a-private-key