Explanation:

- Let P(E) be the probability of passing English = 80%.

- Let P(H) be the probability of passing Hindi = 70%.

- P(F) is the probability of failing both subjects = 15%.

- Use the formula for the union of two events:

P(E ? H) = P(E) + P(H) - P(E n H).

We know P(E ? H) = 100% - P(F) = 85%.

- So, 85% = 80% + 70% - P(E n H).

Solving, P(E n H) = 65%.

- Passing at least one subject is 85%, meaning 15% failed both.

- Students passing both English and Hindi are 65%.

- Therefore, students passing exactly one subject = 85% - 65% = 20% (failed in only one).

- Option 2: 20% is Correct.