NL100: Nut straight, 3betted pot - extracting question

[ranka]

MP1: 27/19/3 - 85 hands

PokerStars No-Limit Hold'em, $1.00 BB (8 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

UTG ($158.35)
UTG+1 ($109.85)
MP1 ($197.15)
MP2 ($304.70)
CO ($102)
Button ($97)
Hero ($128.75)
BB ($98.50)

Preflop: Hero is SB with K[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/heart.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">MP1 raises to $6</font>, <font color="#666666">3 folds</font>, <font color="#CC3333">Hero raises to $18</font>, <font color="#666666">1 fold</font>, MP1 calls $12.

Flop: ($37) Q[img]/images/graemlins/heart.gif[/img], T[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks or bets?