How + Adjective Questions :
How + adjectives can be used to indicate a quantity, or a degree of something.

Examples

Much = Used to describe uncountable nouns.
– How much milk do we need ?

Many = Used to describe countable nouns.
– How many pairs of shoes do you have ?

Difficult = the difficulty of something
Difficult  how difficult  how difficult is your homework ?

Deep = the depth of something.
Deep  ⇒  how deep ?  ⇒ how deep was the swimming pool ?

Old = the age of something
Old  ⇒  how old ?  ⇒  how old is your father ?

Wide = the width of something
Wide  ⇒  how wide  ⇒  how wide is the boat ?