200 books x 30 boxes = 6000 books
6000 books x 20 shipping crates = 120,000 books
Just keep multiplying
It is called a long ton which is 2,240 pounds where a ton is 2,000 pounds.\
Fermat's little theorem states that

≡a mod p
If we divide both sides by a, then

≡1 mod p
=>

≡1 mod 17

≡1 mod 17
Rewrite

mod 17 as

mod 17
and apply Fermat's little theorem

mod 17
=>

mod 17
So we conclude that

≡1 mod 17