An investment club invested 5000 at an annual simple interes

An investment club invested $5000 at an annual simple interest rate of 8.4%. How much additional money must be invested at an annual simple interest rate of 10.5% so that the total interest earned will be 9% of the total investment?

0.084(5000)+.105x=(5000+x).09
420+.105x=450+.09x
.015x=30
x=2000
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check
5000*.084=420
2000*.105=210
7000*.09=630