Question 235033
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Let *[tex \Large x] represent the amount invested at 9%.  Then the amount invested at 7% must have been *[tex \Large 8000\ -\ x].


Then the amount of interest earned on the 9% investment must have been *[tex \Large .09x] and the amount of interest earned on the 7% investment must have been *[tex \Large .07(8000\ -\ x)]


The sum of these two earned amounts is given at $660, so:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ .09x\ +\ .07(8000\ -\ x)\ =\ 660]


Just solve for *[tex \Large x] to get the one amount and subtract that from 8000 to get the other amount.


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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