For this to find the median all you do is put the numbers in order from least to greatest. Is there is a odd amount of numbers then it is the number in the middle. If there is an even then you find the two numbers in the middle and do by .5
In this case there are an even amount of numbers. So..
Put the numbers in order.
-70,-64,64,66,70,73
So the two numbers in the middle are 64 and 66.
The median is: 65