Okay so
If there are 28 white ducks, and twice as many brown ducks thats
28x2=56
So the total amount of ducks is 56(brown)+28(white)=84
Then, if half the amount of while ducks fly away thats
84-14=70 (You get 14 by diving the amount of white ducks by 2 28/2=14)
Therefore, there are 70 ducks in the pond after half the amount of white duckies fly away.