Will I escape?
First you might be ambushed. You cannot be ambushed if you are invisible (regardless of the encounter monsters), if pass a Perception-1 in 100 roll, if you pass a 150 difficulty Alertness check, if you are a level 6 druid or a level 25 merchant (undocumented ability), or if you have the Scout talent and pass a 1 in 10 roll. Even if you meet none of those requirements, monsters only have a 1 in 30 ambush chance. They get an additional 1 in 15 if you are Cursed and a 1 in 8 on top of that if Doomed, for a combined ambush chance of 21% if cursed and doomed. If this happens, tough luck - you can't escape and the monsters start next to you, so no shooting.
Next, you get the chance to sneak. You successfully sneak (Stealth + Survival) times in 1000 tries. If you are invisible, you will successfully sneak an additional 500 - XL * 10 times (yes, XL hurts you here). Successful sneaking increases escape chances and allows you to spring an ambush of your own.
If you choose to ambush, a variable is increased by 50 times your Stealth skill and 30 times your Survival skill; this is probably the amount monsters are surprised in some way. If you fight or ambush, things end here.
You have five checks to escape an encounter. Only one of them needs to pass.
First, if you are a level 6 druid or level 25 ranger, you escape automatically.
Next, the encounter's first Escape number is a flat chance of escape. This chance is tripled if you made a successful sneak.
Next, if you are invisible, you get a chance to escape of the encounter's second Escape number. No tripling here.
Next, you escape if you make a successful Stealth check. The difficulty of this check is 200 minus the lesser of the escape numbers.
Next, you can escape automatically 1/3 of the time with the Scout talent.
If you fail all that, you have to fight. Sorry!