I spent yesterday and today doing the research, programming and writing up an article on the "Slingo Bonus Bet 21" blackjack side bet. This wager is nearly extinct and there's a good reason for that. The first draft of the article is complete, but I need to double-check everything. So for today, imagine you were an AP and stumbled on this side bet in a little casino you were visiting for a few days, with a $10 maximum bet on each of the 10 possible wagers.
First step, go to Google and see if you can locate any information on advantage play against this bet. Then consider the individual parts of it and see if there is documented advantage play against any of the pieces of it. Then give some consideration to its potential vulnerability to card counting. Try and gauge the magnitude of the potential profit for an AP, if any. In doing this exercise, you are free to imagine building a team of APs to occupy a table. You will be playing a six-deck game dealt to 260 cards (1 deck cut off).
At the end of the exercise, if you want to get on to the first flight to play full-time against this wager (even if you work FOR the casino industry), then you are on the right track.