You are playing hold'em and have QHJH. Your only opponent raised before the flop and then bet the flop. On the turn the board is A©K©7§2.¨There is £100 in the pot., which he bets. If you call it is all-in. Should you pass or call?

You can assume you are losing. You will win if you hit a heart or king on the river. This is 12 cards. Don't make the mistake of counting the K© twice. You can see 6 cards and thus there are 46 unknown. You win 12/46, about 25% and are a bit better than 3/1 against.

But you only win £200 for the £100 to be risked. It is a clear pass. Do you have to do such arithmetic at the table? No at all, you only need to know that yoy should never call with less than 15 outs (winning cards) in this situation.