I come to the experts on everything I can think of help. My
teacher-wife asked me if she was calculating this correctly. I didn't
think so. What's the answer and why/how?

Chapter tests count for 60% of the final grade. Mid-term and final
tests count for 40% of the final grade. Scores for chapter tests were
80, 50 and 69. Mid-term and final tests were 80 and 90. What is the
final grade. One of us says 73.8 and the other says 80.7

Thanks