So, you can do this like this:
let damageAfterArmor, damageAfterArmor2;
damageAfterArmor2 = damage * (100 - Armor2) / 100; // Damage mitigated by Armor2 (percentage)
damageAfterArmor = damageAfterArmor2 - Armor; // Damage mitigate by Armor
hp = hp - damageAfterArmor;