Hi,
Follow the approach below:
1. List the elements of the sets E, F, and E intersect
F.
2. Find P(E occurs), P(F occurs) and P(E and F
occur).
3. Apply the result P(E or F occurs) = P(E occurs) + P(F
occurs) - P(E and F occur).
Thanks.
Cheers,
Wen Shih