Answer:
192.5 acres.
Step-by-step explanation:
Total area of farm the farmer had = 420 acre.
Of these he did not plant full but only 7/12th of the total acres.
Planted area with corn = 7/12(420) = 245 acres
Of these 245 acres, 3/14th was affected by crop and the remaining part would be healthy
crop affected by disease = 3/14 (245) = 52.5 acres
Hence healthy corns = area planted for corn-diseased part of area
=245-52.5
= 192.5 acres