Nina, this is the solution to the problem:
Area of land on the farm = 25 acres
Corn = 68% of the land
In consequence, the area where the owners did NOT plant corn is:
100 - 68 = 32%
Now, we can calculate the 32% or 0.32 of the total land, this way:
The owners did not plant corn on 0.32 * 25 acres
The owners did not plant corn on 8 acres