(i) By transferring 20 marbles from A to B and 20 marbles from C to B.
(ii) By transferring 20 marbles from A to B and 10 marbles from C to B.
(iii) By transferring 40 marbles from A to B and 20 marbles from C to B
(iv) By transferring 30 marbles from A to B and 30 marbles from C to B.