SOLUTION: Here is the problem: 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 intrest. How m

Question 180131: Here is the problem:
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 intrest. How much was invested at 7%?
I can honestly say that I am beyond stuck I don't even know where to start on this problem. Please Help!!! :-)
Answer by Mathtut(3670) (Show Source): You can put this solution on YOUR website!
let x and y be amounts invested at 7% and 9% respectively
:
x + y = $12,000..................eq 1
x * 0.07 + y * 0.09 = $970.......eq 2
rewrite eq 1 to x = $12,000 - y and plug that value into eq 2
:
($12,000 - y) * 0.07 + y * 0.09 = $970
:
$840 - 0.07y + 0.09y = $970
:
0.02y = $130
$invested at 9%
:
$invested at 7%
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