Quote:
http://forumserver.twoplustwo.com/40...03-2010-a-319/
Are parlays and teasers bad bets?
Generally yes, parlays and teasers are -EV compared to straight bets. Although correlated parlays can be +EV, and teasers through certain numbers (through the 3 and 7) in the NFL (called Wong Teasers or "basic strategy teasers) can be +EV as well. Beyond that, stay away from parlays and teasers unless you are just out for fun.
Sounds like you are just out for fun, so as long as you aren't risking too much, it should be fine. ML parlays (of favorites) allow you to follow more games (I assume you watch/follow games you bet?) and keep your risk small.
To actually answer your question, you need to determine the % of Team X and Team Y winning, and then decide if your payout justifies your risk.
Do it like this:
Team X: should win the game 80%
Team Y: should win the game 70%
So, they will both win 80% x 70% = 56%.
So, if you are risking 100 to win 91, you are making money. If you are risking 100 to win 75, you are losing money.
Or, parlaying a losing ML with anything is a bad bet