There were 25 birds on two branches. After a while 5 birds from the first branch flew over to the second and after a while longer 7 birds from the second flew away. In that moment on the first branch there were twice as many birds than on the second. How many birds were there on each of the two branches in the beginning?
Solution
When the 7 birds flew away from the second branch the total number of birds on both branches was . Because in that moment on the first branch there were twice as many birds than on the second, there were birds on the second branch, and on the first one were birds. Hence, before the 7 birds flew away from the second branch, there were birds on it. In the beginning, before the 5 birds flew from the first to the second branch, on the second branch were birds and on the first were birds.
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