Question 840759
 
x = amount at 5%
y = amount at 8%

then X + Y = 1400  ---1
Let the number of years be 1.
simple interest of X = (X*1*5)/100 => 5x/100
Simple interest of Y = (Y*1*8)/100 => 8y/100
Given that his total annual returns from these investment was 100 then,

5x/100 + 8y/100 = 100  ---2

Multiplying equation 2 by 100

5x + 8y = 10000  ---3

Solving equ 1 and 3

  8x + 8y = 11200
  5x + 8y = 10000
      ----------------
      3x      = 1200
            x = 400
then Y = 1400 - 400
Y = 1000

therefore 400 invested at 5% and 1000 invested at 8%.