Spam and Lake have the mission to destroy the Star Joke Spam

Spam and Lake have the mission to destroy the Star Joke. Spam’s probability of success on any given try is .7, while Lake’s is .8. Spam and Jake will each be able to make just one try, and they decide that Spam will be first. What is the probability that the Star Joke is in fact destroyed? (Answer should be .94, but i don\'t know how)

Solution

P( It is distroyed ) = P( spam s try destroyed the star jake) + P( spam is failed , now lakes turn) = 0.70 + (1-0.70)*0.80 = 0.70+0.24 = 0..94