Answer:
The correct answer is: [A]: " -(-21) = 21 " .
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Step-by-step explanation:
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Let us examine the answer choices given.
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Choice: [A]: " -(-21) = 21 . This is correct;
→ since a "negative value of negative value" is a "positive value" ; as shown in this case. The equal sign holds true, since the
"negative of a "negative value" is equal to the "positive value" of that same "positive value equivalent."
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Choice: [B]: " -(-21) = -21 . This is incorrect. As explained above:
→ a "negative of negative" is a "positive value" .
This answer choice shows that a "negative of negative"; is a "negative" :
→ which is: INCORRECT.
→ Rule out: "Choice: [B]."
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Choice: [C]: " -(21) = 21 . This is incorrect. The "negative" value [of a positive integer is not equal to the "equivalent positive value" of that same integer.
→ Rule out: "Choice: [C]."
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Choice: [D]: " (-21) = 21 "; This is incorrect. In a conceptually similar way as explained above—(for "Answer Choice: [C]" — the "negative value equivalent" of an integer is NOT equal to the "equivalent positive value" [of that same integer.].
→ Rule out: "Choice: [D]."
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The correct answer is: [A]: " -(-21) = 21 " .
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Hope this is helpful to you!
Best wishes!
which is the final answer. 
means "not" so writing 
means "not q" which is the complete opposite of q.