Answer
The truth value of the statement “Fred and John are happy” is 0.4
The truth value of the statement “Neither Fred nor John is happy?” is 0.2
Work Step by Step
The truth value of the conjunction is the minimum of the truth values.
In the first sentence they are 0.8 and 0.4, so their minimum is 0.4.
In the second one they are 1 - 0.8 and 1 - 0.4, that is 0.2 and 0.6.