
is true when

is false, or when both

and

are true.
Similarly,

is true when

is false, or when both

and

are true.
It seems that you are given that
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and
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. According to the truth table given above, these can both be true only when one of

is true and the other is false.
On the other hand,

is true when either or both of

or

is true. This is satisfied by the implications in the hypothesis, so

must be true.