Resistance to Cold, Fire, Lightning, Poison, etc

[Immaculate]

Are the resistance bonuses form several sources cumulative or do you simply get the best one.

Lets say a thug use a fire brand and cast that nature spell (don't remember the name) that gives 50% elemental resistance across the board, does said thug get 100% fire resistance or 50%.

What about a firebrand and a burning pearl (both 50% right?) so is that gonna add up to 50% or 100% (or something wonky in between?)

What about the same item twice (like two fire brands)?

Thanks,
i.