Subtracting 999-100

Date: Tue, 6 Dec 94 14:55:39 PST
From: michael laue
Subject: math

Dear Dr. Math, 

My name is Michael Laue.  I want to ask you a question -- it is   
what is the answer to this:  999-100?

Date: Wed, 7 Dec 1994 00:06:55 -0500 (EST) 
From: Dr. Sydney
Subject: Re: math

Dear Michael,

Hello there!  Thanks for writing Dr. Math!  To subtract numbers I find it
easiest to write them on top of one another so that the right hand sides
line up, like this:

     999
    -100
   ------

Then you subtract as you would with simpler numbers, starting with the 
right side. 9 - 0 is 9, and 9 - 1 is 8, so you get:

  999
 -100
 ----
  899

Does that make sense?  You can always check your answer by adding the 
answer and the number being subtracted -- you should get the number 
from which you are subtracting.  So check:  is 899 + 100 = 999?

I hope this helps.  Write back if you have any other problems.

Sydney