We can solve this by working backwords.

At the end each box has 160 oranges so before we move 1/6 of the oranges from box C to box A there must be (128,160,192) oranges in the boxes A,B and C. So before we moved 1/5 of the oranges from box B to box C we must have had (128,200,152) oranges in the boxes. So before we moved 1/3 from A to B we must have had (192,136,152) oranges in each box which is the final answer