What does it mean when there is a number above and below a dash in algebra?

The notation of a bar (vinculum, or overbar) over a whole number  

doesn't seem to be very common.  Here are some possibilities as to  

what it could mean:

It is sometimes used as a grouping symbol, as in a fraction:

                                 __

  3 + 1  x  5     =  20             so 67  =  67

I have also seen it used to refer to the average:

                      _                __

  x = {1,2,6},   x  = 3             so 67  =  67  

  (the average of one number is itself, of course).

I have also heard that it can be used to mean "1000 times whatever is

underneath", especially with Roman numerals - see the following Web  

page, Final Answers by Gerard P. Michon:

x = -2

y = 848

step-by-step explanation:

plug in the numbers

answer: it's upside down and i can't read it

step-by-step explanation: