What formula do I use? Step by step would help me study these problems

The probability that a complex assembly line works correctly depends on whether the line worked correctly the last time it was used. There is a 0.7 chance that the line will work correctly if it worked correctly the time before, and a 0.6 chance that is will work correctly if it did NOT work correctly the time before. What is the long range probability that the line will work correctly? The long range probability that the line will work correctly is | . (Type your answer as a fraction reduced to lowest terms.)