An unbreakable book cipher?
Book ciphers are well understood and this seems like a fairly minor variation. Following Kerchoff's Principle we separate the key being the book and the arithmetic operator and numbers and the rest. Picking a random number for fourth position makes no difference in this regard. But even if we let that be a secret to it makes little difference. Humans are lousy at picking random numbers and this will be apparent.

Multuplying by a constant is also a really bad idea. It will be very quickly apparent all numbers in a certain position are a multiple of constant and will be devided by it.

Subtracting or adding a number from row or character number will also be apparent after collecting sufficient data by observing the skewed range. such an addition will be slightly harder regarding page number due to higher cardinality of page numbers but won't necessarily be an issue see next.

Humans doing a poor job picking random numbers. Many people who use book ciphers flip forward a bit from where they are or start reading from the start of the page. This means rare letters will require on average more skipping forward leading to some leakage.

Also the book itself may be selected from a limited set of books can make the book itself guessable.  Given a large library of online books brute forcing such a cipher isn't all that difficult.

If you do not want to mark the book making it physically obvious it is a cipher key it is difficult to prevent repetitions when randomly selecting characters.

If the book is considered a secret not chosen from a limited selection available at your local book store for instance and the person using it picks a random starting point in the book for each letter and seeks the next matching one and marks off each used letter to prevent duplicates then it is a fairly secure cipher even without the additions described.

In reality most book ciphers have been and will be broken.