Question

Part of $3000is invested at 12%, another at 13%, and the remainder at 14%. The total yearly income from the three investments is $400. The sun of the amounts invested at 12% and 13% equals the amount invested at 14%. Determine how much is invested at each rate.

Answer 1

Answer: 500 investigated @ 12%, 1,000 @ 13%, 1,500 @ 14%. 
Process: 
Suppose $x investigated at 12%, $y @ 13%, $(x+y) @ 14%. 
According to the question we can set up the equations: 
x+y+x+y=3000
0.12x+0.13y+0.14(x+y)=400
Solve it: x=500, y=1,000. 
So x+y=1,500.