What to do here? Raised pre to 11 with 77 in position. Folded around to medium position player (tight, aggressive) who calls. Flop 2,3,6... He checks and I bet 15 and get flat called. Turn is a 6, MP player bets 22 and I call. River is a J. I check/call a $45 river bet. He has a set of 3's. This board was tough but I guess this comes down to knowing the opponent? Thoughts?