Answer: It would be dug 9 feet deep hole in the ground.
Explanation:
Since we have given that
On the first day , they dug a hole of length = 3 feet
On the second day, they dug a hole of length = 2 feet
On the third day , they dug a hole of length = 4 feet
Since all the above integers are negative integers as they are length beneath the ground.
So, Sum of negative numbers would be

And the total sum would be

Hence, it would be dug 9 feet deep hole in the ground.