User blog:Mamerge/Do they stack that way or this way?

Okay so I came across a question and I don't know how to answer it. It was
===Suppose you have a 4 star rainbow leader, and friend with the same leader skill ===

Or is it:
===with the first boost of 25% it's  100*1.25=125 Then the second boost of 25% 125*1.25=156,25. ===

===How do they calculate it? Former or latter? ===