Would a pack of coyote's attack a 150 Lb Neopolitan Mastiff ? I'm guessing they wouldn't because at least one coyote would die.?

There cousins hyenas etc attack lions on an empty stomach so I would say yes 

Coyotes are known to jump large dogs if the circumstances are right.  The dog needs to be alone and far away from humans.  Large dogs in a fenced yard near a house are less likely to be attacked by coyotes than one allowed to roam across the fields.  

Coyote pairs will allow last year's grown pups to hunt this year because it brings in more food for this year's pups.  Then they're kicked out of the family pack to go find mates.  So a coyote pack can be eight to ten strong, which is enough to bring down a big dog without losing a pack member. 

Depends on how many are in the pack of coyotes.  The dog doesn't have any experience in killing or fighting & would end up being torn to pieces by the coyotes.  I would be very afraid for the dog.  It has no experience doesn't know how to protect itself from many coyotes.  Coyotes are very coy & could easily take down the dog if there were enough of them, they hunt in packs.

Coyotes are not social animals by nature and rarely travel in packs,, not saying they never do, they will on occasion form packs,,, nor is it normal for them to attack much larger canines,,, once again, not that they won't, or not that they can't, it's just not usual coyote behavior,, although it should be noted that coyotes can, and have, attacked and killed much larger dogs,, they have been known to kill Great Danes, Rottweilers and Dobermans,, and it should be noted they rarely attack dogs that look like wolves because they have a natural and instinctive fear of wolves. If that were to happen, I would put my money on the Mastiff,,, but you would have massive vet bills afterwards.

Now if you want to talk a pack of wolves,,, they would tear your Mastiff to pieces and have it for lunch.

No. It's too ugly to be attacked.

My dog - not a Mastiff - is 142 pounds, and TWO coyotes attacked her in Arizona.  Does that answer your question?  The pack was around, howling, but TWO attacked.  I have a carry permit.  First shot into the air, they both stopped attacking and ran.

As somebody mentioned,  coyotes rarely go in packs.  They also mate freely with dogs, when they get a chance.  So they regard dogs as the same species, though the mastiff may be a stranger.  They might behave aggressively toward the mastiff to make it go away, especially if they have pups.  And if they are defending pups, and they think the mastiff is getting too close, they might bite.  You could call this an attack, but really it is a defense and is not intended to kill but to scare the intruder away.  Animal control would not consider this as a case of coyote aggression.  

Coyotes rarely travel in packs.

Probably not unless the leader of the coyote pack had rabies and had no sense in its head. And then the rest of the pack would tend to follow the leader

They're not going to go randomly attacking things for no reason, but if they had a reason, then yes