8 out of 4 ball is in left side

Now dividing 50 by (8+4) = 12

We get 4.166, Taking only integer part 4

In 4 turns, he will put 32 balls in right side , 16 balls in left side

In fifth turn , he has 2 ball only

Which he will again put in right box

Therefore total balls in right box = 32+2 = 34 balls