Question 1195905
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x = amount invested at 5%
9000-x = remaining amount invested at 15%


Assuming simple interest is involved (instead of compound interest), we then use this formula
i = P*r*t
where,
P = principal aka deposit
r = interest rate in decimal form
t = number of years


The portion invested at 5% will get us this amount of interest
i = P*r*t
i = x*0.05*1
i = 0.05x
which is what we'll have at the end of the year from this one investment.


The other account yields...
i = P*r*t
i = (9000-x)*0.15*1
i = 1350-0.15x


These two interest subtotals add to the stated annual interest of $520
(0.05x) + (1350-0.15x) = 520
-0.10x + 1350 = 520
-0.10x = 520-1350
-0.10x = -830
x = -830/(-0.10)
x = 8300 dollars was invested at a 5% interest rate


9000-x = 9000 - 8300 = 700 dollars was invested at a rate of 15%


<font color=red>Answers:</font>
Amount invested at 5% = <font color=red>$8300</font>
Amount invested at 15% = <font color=red>$700</font>


Check:
8300*0.05+700*0.15 = 415 + 105 = 520
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