Say I need a net hit of 20 or higher. I get to roll 5d6 base, but I get a bonus dice roll of +3. I only get to keep the 5 highest so I would be rolling "8d6 drop lowest 3 rolls" I want to know what formula I would use to calculate the probability for these kinds of rolls in the future.
Example explaining the skill system:
[skill] Agility 5, [specialty] Dodge 3. I make a dodge roll, so I roll 5d6 (from the skill) +3d6 bonus dice (from the specialty), but I can only keep 5 dice (because of my skill). So I roll 8d6 total, and drop the three lowest rolls, adding the 5 remaining rolls to see my net roll.