Qus 1: 21 pesos
Qus 2: The farmers were served 27 potatoes.
Already eaten-
1st farmer = 9 potatoes
2nd farmer= 6 potatoes
3rd farmer = 4 potataoes.
Remaining potatos share-
1st farmer = 0 potatoes
2nd farmer= 3 potatoes
3rd farmer = 5 potatoes.
Thank you @sampu for the contest, and I invite @hriya and @bull1 to participate in this contest.