Question 1169331
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The governing equation is


    {{{(9+x)/(20+x)}}} = 0.75.


It implies


    9 + x = 0.75*(20+x)

    9 + x = 15 + 0.75x

    x - 0.75x = 15 - 9

    0.25x     = 6

        x     = {{{6/0.25}}} = 24.     <U>ANSWER</U>
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Solved.