Given that there is no information about the players involved, I believe there is no right answer here (I wonder who's answer you're going to accept).
To me it smells like there are 4 possibilities:
- a set
- big/top pair with top kicker (AJ or AT)
- overpair (if he thinks you paired a Ten or a Jack)
- flush draw
The flush draw is at the bottom of the list because it's the least likely.
An important thing to figure out is that, just as you don't have any information about the other players, they don't have any information about you.
Now, his raise is very big, too big even, especially because this is the very first hand: $40 in a $27.4 pot is just a lot.
The dynamic changes a lot because of that 3rd player in the UTG seat. So let's look at the possibilities:
- if you fold, that's that. Your losses are minimal and you might feel a little bad about it :)
- going all-in here is the WORST idea possible. DON'T !! Yes, there's a very big chance that you'll just take it then and there, but if you run into a set of Tens or a set of Jacks, you might just get called and lose everything in the very first hand.
- if you call, the total pot then becomes $27.4 + $40 + $40 = $107.4. The guy in the UTG will have to make a $31 call. Depending on what he has, that amount could give him good pot odds to make the call. Unless he has a monster, this is very unlikely because it's a bad idea to go against 2 players at once in the very first hand. My best guess is that, if you call or raise, there's a chance of at least 80% that the guy in the UTG will fold. If you do call, then you will go to the turn out of position. No matter what the turn card is, a check on the turn will make your opponent bet it in order to steal it (at least a $60 bet, I guess). If you bet on the turn and he raises, then you'll know he's strong (or maybe he's just a very aggressive player ?).
- a raise from you at this point will almost definitely get rid of the guy in the UTG seat except, just as I said above, if he has a big monster (set of Tens or Jacks; overpairs (QQ, KK, AA) are usually a fold here). The problem is that your raise would have to be to a total of at least $80 - $100, which is a too big percentage of your stack. The upside here is that, if he pushes, then you can safely fold. This is a problem because you would lose about a quarter of your stack there. The downside of a raise is that, if he just calls, then it means he's very confident about his showdown value AND you're both kind of pot commited.
Looking at my thought process above, I believe that, in this particular spot, a call on the flop is probably the best decision. Like I said above: this would probably get rid of the 3rd player. I would then make a bet on the turn to see what he does.
