Question

Carol ate 2/5 of the cake. Dima ate 3/5 of the REMAINING CAKE, mom ate the rest.

Answer 1

Carol ate 2/5 of the cake, leaving 3/5 of the cake for others  ( ! )  Note that 2/5 = 10/25, and that 3/5 = 15/25.

dima at 3/5 of this 3/5, or 9/25 of the cake.

Subtract 9/25 from 10/25:  The difference is 1/25.

Carol ate a share that was 1/25 larger than Dima's share.