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Topic: I need help setting up this system of equations
Replies: 1   Last Post: Nov 26, 2008 7:37 AM

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Posts: 1
From: nc
Registered: 11/25/08
I need help setting up this system of equations
Posted: Nov 25, 2008 2:22 AM
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I'm trying to set up a system of three equations. I have two of them, but I can't get the third. Anyone know what to do? Here's the problem:

Jane's employer gave her a bonus of $1600. She decided to invest all the money, some at 5%, some at 7%, and some at 8%. She invested three times more money at 8% than she did at 5%. At the end of one year the total interest she earned was $115.

Here are the first two equations of the system I've found:

x + y + z = 1600
.05 x + .07y + .08z = 115

I'm stumped as to what the third one is. I need the third one to solve and figure out how much money this bitch invested in each. Can anyone help? Thanks in advance.

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