Do evolite and stat increase multiply or add?

Question

If a Pokemons sp def and def are 100 evolite would make them read as 150.

And if I'm understanding stat increases having sp def and def increased by 6 stages would make them 400.

So if a Pokemon has those increased stages AND is holding evolite are its stats at 450 adding the increases or at 600 because they multiply each other?

Answer 1

They are independent and multiplicative. If you have 100 at +6 with a working Eviolite, you apply the +6 to go to 400, then Eviolite makes it 600.