When playing one deck blackjack, in case the dealer doesn't have a blackjack and he stands on a soft 17, if he has a 5 and you have an 8 and 2, your best option would be to double down.
Let's assume for argument's sake that in a game of double deck blackjack, the dealer doesn't have a blackjack while he hits on a soft 17; if he has a 6 and you have an 8 and 5, it would be best to stand.
When you play one-deck blackjack and you believe that the dealer (hits on a soft 17) hasn't reached blackjack yet, if he has a 5 and you have a 5 and 3, odds are you should hit.