The number of chickens to the number of ducks on a farm was 6: 5. after 63 ducks were sold, there were 3 times as many chickens as ducks left.

C:d=6:5
63 ducks sold
then the ratio is not
3:1
so
3:1 times 2:2=6:2
so from 6:5 then 63 weere sold becomes 6:2
therefor 3 duck units=63
therefor
3/63=1/21
1 unit=21
there is not question so I will solve for
1. total number
2. original numbe rof chickens
3. original number of ducks
4. final numbe rofo ducks

total number=total units times number per unit
number per unit=21
ttoal units=5+6=11
21 times 11=231

total=231

chickens=6 units
6 times 11=126

original ducks=5 units
5 times 21=105

resulting number of ducks
2 units
2 times 21=42

total=231
original chickens=126
original ducks=105
final number of ducks=42