Hello! So, there were 67 white ducks and 2 times as many brown ducks flew in the pond. 67 * 2 is 134. Then, half of the white ducks flew out. There were 67 white ducks. 67/2 is 33.5, but you can’t have half of a duck fly away. We would have to round up, so that would mean 34 white ducks flew out, because 33.5 rounds up to 34. 134 - 34 is 100. There are 100 ducks that remain in the pond.
