Oh my gosh,
I need an answer for that as well..
Answer:
0.25
Step-by-step explanation:
Average means 
According to the formula, each student in Mr. Goldwasser's class read

books on average, and each student in Mr. Welch's class read

books on average.
Therefore, the answer will be

-10 and 8 multiply them to equal 80 but if there both negative it will be a positive 80 because if you multiply 2 negatives its postive hope this helps
You know that 7*7 is 49, and 6*6 is 36. Now you know it will be 6._. 6*7 is 42, so think of that as 6.5^2. You know that it will most likely be less than 6.8 since it is so close to being 7*7, which is 4 above your desired number. This leaves 6.6 to 6.8 as your estimate. Personally, I would go straight in the middle and choose 6.7.
I hope this helps!