Given that,
Karen will divide her garden into equal parts. She will plant corn in 12/20 of the garden.
To find,
The fewest number of parts she can divide her garden into.
Solution,
It is mentioned that she will plant corn in 12/20 of the garden.
If we divide both numerator and denominator by 4, it will become:

It means the fewest number she can divide her garden into is 4. 3/5 part is planted with corn and rest 2/5 is not planted with corn plant.