I'm trying to calculate something.

If I have an 80% chance to succeed at gathering an item.

I know each roll is individual. So just having 80% doesn't mean I'm going to roll 8 successful and 2 fails.

So how do I calculate this?

So let's say I have a base 80% success rate. But I mine and fail 7 times, and succeed 3.

How can I calculate the odds of that happening? There must be a formula or something.

Thanks.

Sorry, I'm really not so good at math.