Which expression represents the sum of 2/3m - 1 1/6 and 5/6m - 1 1/3?

First, combine like terms.  In other words, combine (2m/3) and (5m/6).  Note that you'll need to identify and use the LCD here; it is 6.  

Next, combine -1 1/6 and -1 1/3.  Converting those into improper fractions first, we get -7/6 and -4/3.  Again the LCD is 6.  Combine these two fractions.

Now add your two results together and you'll be done.