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There are

ways of selecting two of the six blocks at random. The probability that one of them contains an error is

So

has probability mass function

These are the only two cases since there is only one error known to exist in the code; any two blocks of code chosen at random must either contain the error or not.
The expected value of finding an error is then
Answer:
288 trust me it is 100% right I tried it as an answer an got it right.
Step-by-step explanation:
Answer:
Answer: Janet is 16, and David is 11.
Step-by-step explanation:
Let the ages be j and d.
j = d + 5
j + d = 27
Substitute d + 5 for j in the second equation.
d + 5 + d = 27
2d + 5 = 27
2d = 22
d = 11
Substitute 11 for d in the first equation.
j = d + 5
j = 11 + 5
j = 16
Answer: Janet is 16, and David is 11.