Understanding ML on dogs

[3GCOVERAGE]

I've been betting a little baseball and I get the lines sent as me as the ML on the favorite. How do I know what the ML is on the underdog? To my knowledge I thought that is varies from book to book and can be a different spread between the dog ML and favorite ML. Is there an assumed dog ML based on the favorite's odds (ML)? For example if a the Yankees are -120 are the Red Sox assumed to be +100?

[Easy-Rider 66]

I've been betting a little baseball and I get the lines sent as me as the ML on the favorite. How do I know what the ML is on the underdog? To my knowledge I thought that is varies from book to book and can be a different spread between the dog ML and favorite ML. Is there an assumed dog ML based on the favorite's odds (ML)? For example if a the Yankees are -120 are the Red Sox assumed to be +100?

Probably the case unless the book is dealing dime Lines.