Question

for example if a golem use earthquake the power will be 150 since both golem and earthquake is ground type,
but if you use it on for example a pikachu will the power be 300 or 250 then?

Answer 1

All boni are multiplied.

Base power * STAB * type effectiveness

In case of a super effective STAB earthquake:

100 * 1.5 (STAB) * 2 (effectiveness) = 300

Comments

Also, look at it like this.

60 base, with STAB is 90 X2 is 180.
And you can still look at it like ...

60 base, X2 is 120 with STAB goes to 180.

---

With stab, critical hit, and super effectiveness, you can potentially do 650% dmg increase with a stab, super effective against dual types critical hit.

---

Now go calculate the base power when Victini uses V-generate with choice specs against a parasect with dry skin, scoring a critical. I think this is a quadruple overkill.