23×8-1

23 means 2×2×2 which is 8.  So now we have:

  8×8-1

and since 8 is the same as 81, we now have:

  81×8-1

Now add the exponents of 8 and get

  80

Any positive or negative number to the zero power is 1

Answer:  1

------------------------

You can also do it by using the definition of negative exponents:

23×8-1

23×

8×

   1

Edwin