x + 12%*x + 12%*x is not equal to 1.24x or x + 24%*x

What? Yes it is?

X + .12X + .12X = X + .24X = 1.24X

Am I missing something here?

will not increase regen

You cant say that it's not equal unless you give values, because If I set up a equation and solve for x they can be equal.

Your statement in the title is mathematically false.

What you're trying to get at is whether multiple items that boost a given stat stack multiplicatively or additively.

Additive stacking is the kind you are implying the your title, where a 12% boost+ a 12% boost produces a 24% boost, since the boost is applied to the base value.

Multiplicative stacking is (1.12x)(1.12), where the extra 12% is applied to the current value each time, and so the second boost applies applies the the amount gained by the first boost, and so is slightly larger.

As for the various heal/shield power items, they stack additively with each other. However, the heal/shield bonus only applies to active heals, and not to passive life regen or lifesteal.

Stop copy and pasting your argument. We understand that stacking things the synergize with each other gains a larger effect. And you can't add a % to anything. That means it is a constant and equal to a decimal. So you are left with X + .12 = ? Because you can't add a constant to a variable. That's not how math works and assumes that the % is based off X.

Calm down guys the dude is confused about notations used in economics versus the notation used in league. It is nothing to get heated up over.

1x + 0.12x + 0.12x = 1.24x

I learned that in 7th Grade dude, no need for a college or high school graduation.

I think you might mean 1.12(1.12x) =/= 1.24x

And no, does not increase regeneration from the Heal/Shield power. It's bonus health and mana regeneration stats from the item itself will though. Heal/Shield Power boosts everything except health regeneration.