[Pokerscott]

ok, my take on explaining this graphically and easily [img]/images/graemlins/smile.gif[/img]

1. Draw a square

2. Draw a vertical line down the middle of the square. Left half is A, right half is A'

3. Draw a horizontal line in the square (I drew it about 1/3 up from the bottom so it would look like about 35%). Below the horizontal line is B, above is B'.

4. Your square is now divided into 4 rectangular regions.

5. Finding your answer...
-The top right box is P(A' and B') and equals 20%.
-If the top right box is 20% that means the bottom right box is 30% (remember the right two boxes are A' and must equal 50%)
-If the bottom right box is 30% then the bottom left box must be 5% (remember the bottom two boxes are B and must add to 35%).
-But the bottom left box is P(A and B). Congrats you now know P(A and B) is 5%!

Pokerscott