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A high school mathematical probability and statistics problem 18
The necessary and sufficient condition for (1) A and C to pass at the same time is (1).

So the probability of not less than 8 points is (3/4)*( 1/2)=3/8.

(2) The probability of 2)x = 3 is (3/4) * (2/3) * (1/2) =1/4.

The probability of X=2 is (3/4) * (2/3) * (1-1/2)+(3/4) * (1-2/3)+.

The probability of X= 1 is (3/4) * (1-2/3) * (1-kloc-0//2)+(1-3/4) * (2/3) *

Therefore, the expectation is 3 * (1/4)+2 * (1/24)+1* (1/4) =1and (1/.