SATMathematics Practice Test 1

Since Wyatt can husk at least 12 dozen ears of corn per hour, it will take him no more than $\frac{72}{12}=6$ hours to husk $72$ dozen ears of corn.
On the other hand, since Wyatt can husk at most 18 dozen ears of corn per hour, it will take him at least $\frac{72}{18}=4$ hours to husk 72 dozen ears of corn.
Therefore, the possible times it could take Wyatt to husk 72 dozen ears of corn are 4 hours to 6 hours, inclusive. Any number between 4 and 6, inclusive, can be gridded as the correct answer.