Answer:
  x = $ 16,000  , y = $13,000  z= $11,000
Step-by-step explanation:
given,
Investment amount $40,000
three investments yielding = $3,500
three investments are 7%, 9%, and 11%
second and third are $3,000 and $5,000 less than the first  
         0.07 x + 0.09 y + 0.11 z = $ 3,500  
         x + (x - 3000 ) + (x - 5000) = $ 40,000
            3x = $48,000
              x = $ 16,000
      y = 16000 - 3000 = $ 13,000
      z = 16000 - 5000 = $ 11,000
the investment by each 
  x = $ 16,000  , y = $13,000  z= $11,000