SOLUTION: Walt made an extra $12,000 last year from a part-time job. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at 7

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Question 179363: Walt made an extra $12,000 last year from a part-time job. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at 7%?
Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
let the amount invested at 7% and 9% be x and y respectively
:
x+y=12000............eq 1
.07x+.09y=970.......eq 2
:
rewrite eq 1 to x=12000-y and plug it into eq 2
:
.07(12000-y)+.09y=970
:
840-.07y+.09y=970
:
.02y=130
:
$highlight%28y=6500%29invested at 9%
:
$highlight%28x=12000-6500=5500%29amount invested at 7%