Question 809858
A total of $7100 was invested .

 a certain amount at 7%,-----------x
 twice that amount at 10%,----------2x
the remainder at 12%. ---------------(7100-3x)
annual interest from the three investments = $699

7%x+10%*2x+12%*(7100-3x)=699

multiply by 100
7x+20x+12(7100-3x)=699

7x+20x+85200-36x=699

27x-36x=699-85200

-9x=-84501

/-9
x=9389

amount at 7%,-----------$9389
 twice that amount at 10%,----------2x---------------$18778
the remainder at 12%. --------------- Balance