How many days altogether in the first four months of 1998
2 answers:
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Answer:
See the step-by-step explanation
Step-by-step explanation:
Let c be any element of C. (I'm not sure wether you have to assume that C is non-empt or not)
C is a subset of B. That means that as c is in C, it is also in B. ()
Now, B is a subset of A. It follows that as .
That means c is an element of A. The predicate Q is true for all elements of A, including c.
Because we let c be any element of C, we have proven that the predicate Q is true for all elements in C.