i see what you are saying but my point is, if the question stem says 3/5 passed maths and 1/3 passed english,
then the prob of those who pass both math and english should be
1/3 * 3/5 = 3/15 = 1/5
Unless the stem is implying information that is not given. How can the prob of both be 1/8.
3/5 passed Math could mean that all of the 3/5 passed English as well or none of them passed English.
Let me give you an example:
Let's say we have 6 people, 1 passed Math alone, 1 passed English alone, 2 passed both and 2 failed both
Now if I ask you, How many students passed Math? Will you say 1 or 3?
Similarly, how many students passed English?
Think about it.