Question 1130662: Use two equations in two variables to solve the application.
Peter invested some money at 6% annual interest, and Martha invested some at 12%. If their combined investment was $8,000 and their combined interest was $570, how much money did Martha invest?
Answer by addingup(3677)   (Show Source):
You can put this solution on YOUR website! Martha invested some money at 12%, this is 0.12M
That money is part of the 8,000 joint investment.
Peter invested what's left at 6%, this is 0.06(8,000 - M)
.
0.12M + 0.06(8,000 - M) = 570
0.12M + 480 - 0.06M = 570
0.06M = 90
M = 1,500
Martha invested $1,500
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