About a fifth of the potato crop was ruined by flood another undamanage potatoes spoiled while being hauled to market How much original could farmer sell at prod?

Flood ruined 20% of the crop, which means 100 * 20% = 20 units were ruined.

So, 100 - 20 = 80 units were left.

Now, let's say x units spoiled while being hauled to the market.

Therefore, the farmer could sell 80 - x units at the market.