Answer: The number is: "2" .
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The expression is: 2 − (½)x = (½)x ; 
 → in which "x" is the "unknown number".
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Step-by-step explanation:
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Given: 
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"Two decreased by a half of a number is one-half of the number" ; 
Let "x" represent the "unknown number" for which we wish to solve;
Write the expression as:
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" 2 − (½)x = (½)x " .
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Note: Add "(½)x" to EACH SIDE of the equation:
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2 − (½)x + (½)x = (½)x + (½)x ;
to get:
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 → 2 = 1x ; 
 ↔ 1x = 2 ;
 
 ↔ x = 2 .
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Answer: The number is:  " 2 " .
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