Question 1189302
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I add 12 to a certain number and then double the result. The answer is 42. Find the original number. 
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To solve the problem, go backward:


<pre>
    Divide 42 by 2 to get 21.

    Subtract 12 from 21 to get 9,   which is your  <U>ANSWER</U>
</pre>

Solved and explained.