let say that if a NPC got 40% magic resist. so the damage = dmg x ( (100-40) / 100 ) = dmg x 0.6
so for a weakness of magic of 40% that reduce enemy resist wil be damage = dmg x ( (100 - 40 + 40) / 100 ) = dmg x 1 or maybe we can just use dmg x 0.6 / 0.6
for enemy without magic resist can i just use the formula of damage = dmg / 0.6? Also if i have a weakness to magic poison of 90%. does that make it dmg / 0.1? so a dmg of 90 Thunderbolt will be 900 damage each hit?