The number of chickens raised by Uncle Li is one third of that of ducks. Later, he bought 15 chickens. At this time, the ratio of chickens to ducks is 5:6. How many ducks does Uncle Li raise?

The number of chickens raised by Uncle Li is one third of that of ducks. Later, he bought 15 chickens. At this time, the ratio of chickens to ducks is 5:6. How many ducks does Uncle Li raise?

The original chicken: Duck = 1:3 = 2:6
After buying 15 chickens, the ratio becomes 5:6, which increases by 3 / 6, that is, 1 / 2 of the number of ducks,
So there were 30 ducks and 10 chickens
15/(5/6-1/3)=30