The data represent the number of phone calls received over a 70day period.
day 1 2 3 4 5 6 7
calls received 5 2 9 8 3 1 0
what is the mean number of phone calls received?

Are you talking about 7-day period instead? Or is that really 70? 

Anyway, the mean number of phone calls received over the period of time given would be 4 calls. I got to this answer through adding all of the calls and dividing them by the number of days. 

The answer is 10. and if you go by pemdas you would 1. multiplication 2. division 3. addition 4. subtraction