Question 840868
Let the amount invested at 6% and 5% annual interest be x and y. the number of years be 1.

the x + Y = 24000 ---- 1
and simple interest for x is (x*1*6)/100 => 6X/100
simple interest for y is (y*1*5)/100 =>  5y/100
Given that he recieves an annual returns of $1,380, then
6x/100 + 5y/100 = 1380  --- 2

multipling equation 2 by 100

6x+ 5y = 138000  --- 3

Solving equ 1 and 3

1*6  6x + 6y = 144000
     6x + 5y = 138000
     ----------------
          y  = 6000
then x = 24000 - 6000 => x = 18000

therefore 18000 is invested at 6% and 6000 is invested at 5%.