Let's solve this problem by working backwards.
Since Farhan gave half of his marbles last round and he now has 25 marbles, he had 25 x 2 = 50 marbles in the third round.
Darius has 45 - 25 = 20 marbles in the third round as well.
Ellen gave a fourth of her marbles during the second round and now has 30 marbles left. This means that 3/4 of her previous marbles = 30, so she has 30 x 4/3 = 40 marbles in the second round.
Ellen also gave 10 marbles to Farhan during this round, so Farhan had 50 - 10 = 40 before then.
Darius gave 1/5 of his marbles and ended up with 20 marbles. This means that Darius originally had 20 x 5/4 = 25 marbles.
Ellen received 5 marbles and ended up with 40 marbles, so she originally had 40 - 5 = 35 marbles.
Let's now write down the number of marbles each person has after working backwards:
Ellen has 35 marbles.
Darius has 25 marbles.
Farhan has 40 marbles.