Holding Trips against a flush draw

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you can look at it however you want.

If you hit trips, he's down to 8 outs anyway on the flop since you are either stealing one in your hand (or taking away an out for your boat), then on a non-spade turn, he loses another. So against trips he'll have 7 outs going to the river if he hasn't made his hand.

If he hits on the turn, he doesn't need outs because he has made his hand. If anything he'd hate to see another flush card unless he has the Ace. You'll have 10 outs to improve if he hits.