math
posted by crissy .
Suppose the probability that a construction company will be awarded certain contract is .25, the probability that it will be awarded a second contract is .21, and the probability that it will get both contracts is .13. What is the probability that the company will win at least on of the two contracts?

there are 3 scenarios
1. win the first, lose the second > .25(.79) = ...
2. lose the first, win the second > .75(.21) = ...
3. win the first, win the second > .25(.21) = ....
add them up 
What about the number given, .13 for get both contracts? Wouldn't that contradict the third scenerio?

.33