The correct is answer is A: The main idea of your essay
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You need a hyphen when a number is written out from numbers 1-99. So in the case, the answer would be A.
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Answer:

Explanation:
A fraction is in simplest form when the numerator (top) and denominator (bottom) cannot be any smaller, while still being whole numbers.
To simplify a fraction, divide the numerator and the denominator by the greatest number that will divide both numbers exactly (they must stay whole numbers). To identify the greatest divisor, factorise both numbers.
Since

you can divide the numerator and the denominator by 
