A man invests $5500 dollars in three accounts that pay 5%, 8%, and 9% in annual interest respectively. He has two times as much mondy invested at 9% as he does at 8%. If the total interest earned for the year is $449, how much is invested at 5%?
.05*FIVE+.08*EIGHT+.09*NINE=449
NINE=2*EIGHT
NINE+FIVE+EIGHT=5500 are the three equations.
You can use substitution, or other methods.