All you have to do is take the 30% chance of you HAVING to stop at the first light and find the chance that you won't have to stop at the first light, which is 70%, or .7. Then you take the chance of having to stop at the second light which is 80%, and find the probability of NOT having to stop there, which is 20%, or .2. Then you multiply the probabilities of not having to stop, which equals .14.
