Maybe you can study it or figure out a trick. I usually study with my sibling, but if you don't have any, friends or other family. I am sure they won't mind. Also, maybe making flashcards, those work well.
Also, you can print out worksheets and make your brain remember. PRACTICE!
The sum of all the measurements is just the average times the number.


So if the average of all 92 is 7 the sum of those is

The average of the last two is 7.2 so their sum is

That means the sum of the first 90 is

so the average of the first 90 is

cm
Answer:
C. $20,000
Step-by-step explanation:
2,824*$7.50=$21,315