Answer:
she invest $18,500 at the 17% rate and $15,500 at the 20% rate.
Explanation:
Suppose that you invest some quantity A to an invest rate of x%
At the end, the amount you will have is given by:
Amount = A + A*(x%/100%)
Where:
A*(x%/100%) is the interest income
So, here she initially has $34,000
And she invest some quantity X to a 17% and a quantity Y to 20%
Then we have:
X + Y = $34,000
And we know that her total anual income is $6245
X*(17%/100%) + Y*(20%/100%) = $6245
Then we have a system of two equations:
X + Y = $34,000
X*(17%/100%) + Y*(20%/100%) = $6245
First we can rewrite the second one to a more simpler form:
X*(0.17) + Y*(0.20) = $6245
Now we can isolate one of the variables in the first equation to get:
X = $34,000 - Y
Now we can replace that in the other equation to get:
( $34,000 - Y)*0.17 + Y*0.20 = $6245
Now we can solve this for Y:
$34,000*0.17 + Y*(0.20 - 0.17) = $6245
$5,780+ Y*0.03 = $6245
Y*0.03 = $6245 - $5,780 = $465
Y = $465/0.03 = $15,500
And X = $34,000 - Y = $34,000 - $15,500 = $18,500
So she invest $18,500 at the 17% rate and $15,500 at the 20% rate.