the peasant originally had 21 pesos

27 potatoes were served. The first farmer ate 9, the 2nd farmer ate 6 and the 3rd farmer ate 4.

For all to get equal parts, this how the remaining eight should be shared.
1st farmer = 0 potatoes
2nd farmer= 3 potatoes
3rd farmer = 5 potataoes.

I invite @verdad and @phlexygee