The daily low temperature readings for a five-day period were as followed - 13, - 5,6, - 7, 9 find the average low temperature for the five day period

First add the numbers together:

-13 + (-5),6, (-7),9=-10

Then divide that number by the total # of numbers, which is 5

-10:5=-2

The average low temperature is - 2.

... which is 6th grade stuff, so I am having a hard time believing, that you are in college and/or are having problems with this.