How do I calculate a bet of a running total ?

Thank you for the help.
Lets say that I bet $ 4 with ratio 2.0 (the ratio is constantly changing according to the card that appears now, assume first card).
Then I want to bet on the second card in $ 8 that includes the $ 4 profit.
Suppose second card appears at a ratio of 1.3 profit together are so 8 times 1.3 gives 10.4.
How do I calculate the total price up to the card that appears now ?
How do I calculate the total profit including the initial  bet at each round ?

Thanks

MySTER