Peter invested some money at 6% annual interest and martha invested some at 12%. If their investments is $6000 and their combined interest was $540. How much money did martha invest?

Answer 1

Let Peter's investment be x
then Martha's investment is 6000-x

solve:

.06x + .12(6000-x) = 540
6x + 12x(6000-x) = 54000

I am sure you can finish it.

Answer 2

4000

Answer 3

3000