I can only help you with the rare chance at the moment, but I'll see about helping with the relic chance in the future.
The base rate of finding a rare is 2.22%. The bonuses given from your equipped items are added to this, for example if you had +50%, then it would be: 50% of 2.22% = 1.11% which would then be added to the base rate (2.22%) to give a total of 3.33% chance of finding a rare item.
To find out how much your items would give:
1. Work out the total percentage bonus (92%)
2. (2.22 / 100) * your_percentage + 2.2 = total.
(2.22 / 100) * 92 + 2.2 = 4.2%
Another way to do this, would be: 1.92 * 2.22 = 4.2%