5 * 4 divided by 2 - 4²

Replace the 5 * 4 by 20


   20 divided by 2 - 4²


Using PEMDAS, we do the
exponentential 4² first
and get 16. So we replace
the 4² by 16, and we have


   20 divided by 2 - 16


Now we combine the 2 and
the -16 and get -14, so
we replace the 2 - 16 by
-14, and now we have:


  20 divided by -14


Now "divided by" means OVER,
so we put 20 OVER -14:

       20
     -----
      -14

That's a postive divided
by a negative so the 
answer will be negative,
so we can put a negative
sign out front:


        20
    - -----
        14

and then we reduce the
fraction to lowest terms
by dividing numerator
and denominator by 2

       10
    - ----
        7

You can leave it that
way because in algebra,
"improper" fractions
are quite "proper". LOL

Edwin