Two teaching methods, A and B, are implemented for learning Spanish. There is a 70% chance of successfully learning Spanish if method A is used, and an 85% chance of success if method B is used. However, method B is substantially more time consuming and is therefore used only 15% of the time (method A is used the other 85% of the time). The following notations are suggested: A: Method A is used.
B: Method B is used.
L: Spanish was learned successfully.
A person learned Spanish successfully. What is the probability that he was taught by method A?