What grade do you have to get on the final to maintain an average of at least a 90 if you have grades of 85 and 86

If your final is worth 15% of your grade and you have an 85 you need to score 118.33%. If you have an 85 and the final is worth 20% you need a 110%. If you have an 86 and the final is worth 15% you need 112.67%. If you have an 86% and the final is worth 20% you need a 106%. Good luck