How do I combine two probabilities- Pacers

#1
For arguments sake suppose I handicapp the Miami Heat to have a 60 percent chances of winning tomorrow irregardless of point spread. The expert handicappers, using a system different than mine have Miami at 67%. If the two systems are equally weighted, is this a good bet to make. How do I combine two nonconnected probabilities to get an overall probability given a payoff at 67% or 67 cents per dollar bet?
 
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