What does this simple rebus mean?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

What can go through glass without breaking it?

What came first, the chicken or the egg?

Can you find the ages of a son, father and grandfather based on the following facts?
The sum of the ages of grandfather, father and son is 140 years.
The age of the son in months is the same as the grandfather in years.
The age of the son in days is the same as the father in weeks.

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

The answer I give is yes, but what I mean is no. What was the question?

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

Find the number of squares in the below-given picture.