Lucky numbers

When we toss a coin, there is a 50% chance for a tail and 50% chance for a head. If we assume that, we have the opportunity to bet that the next flip will be tail and the payoff will be $1. So, based on that example the mathematical expectation is:

(.5)(1)+ (.5)(-1)=0

For each game the mathematical expectation of any bet can be calculated by multiplying each probable loss and gain by the possibility of that loss and gain. After that we have to add the two digits.