SOLUTION: Equal amounts are invested at 4%, 7%, and 9% annual interest. If the three investments yield a total of $720 annual interest, find the total investment. Please show all work, Tha

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Question 343472: Equal amounts are invested at 4%, 7%, and 9% annual interest. If the three investments yield a total of $720 annual interest, find the total investment.
Please show all work, Thanks much
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let each equal investment equal x.
%284%2F100%29x%2B%287%2F100%29x%2B%289%2F100%29x=720
4x%2B7x%2B9x=72000
20x=72000
highlight%28x=3600%29
Each equals x, the total would then be highlight_green%283x=10800%29.