Question 1147008
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Let x be the amount, in dollars, invested at 7%.


Then the amount invested at 8% is 2x dollars,

and  the amount invested at 9% is 3x dollars.


Then the equation expressing total interest of three accounts is


    0.07x + 0.08(2x) + 0.09*(3x) = 200   dollars.


Simplify


    0.07x + 0.16x + 0.27x = 200

    0.5x = 200

    x    = {{{200/0.5}}} = 400.


<U>ANSWER</U>.  $400 invested at 7%;  $800 invested at 8%  and  $1200 invested at 9%.


<U>CHECK</U>.  0.07*400 + 0.08*800 + 0.09*1200 = 200 dollars,  which is PRECISELY correct (!)
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Solved.