Question 115899
.09x+.10*2x+.11*3x=2790
.09x+.20x+.33x=2790
.62x=2790
x=2790/.62
x=$4,500 invested @ 9%
2*4,500=9000 invested @ 10%
3*4500=13500 invested @ 11%
proof
.09*4500+.1*9000+.11*13500=2790
405+900+1485=2790
2790=2790