1. Let the current average be represented as C = 85\% .
2. Let the final exam score be represented as F , where the maximum is 100%.
3. The final exam counts as 20% of the final grade, and the rest of the coursework counts for 80%.
4. The overall grade can be calculated by:
\text{Overall Grade} = 0.80 \times C + 0.20 \times F
5. Substitute the current average into the equation:
\text{Overall Grade} = 0.80 \times 85 + 0.20 \times 100
6. Calculate the overall grade:
\text{Overall Grade} = 68 + 20
7. The best course grade your friend can earn is:
88\%