Percentage stacking.

With spells that stack with percentages I had a question how exactly they stacked.

For example, if I attack someone and have lighting storm, fear, and demoralize all with say 10% modifiers would they add together, or multiply out?

ie
Add (50*(1+(10+10+10)/100) = 65% of fleeing.

Multiply (50 *1.1*1.1*1.1) = 66.5% of fleeing.