Question 1178800
.
<pre>

       A
+
    B  B
------------

 A  D  D



<U>ANSWER</U>.  A = 1;  B = 9;  D = 0.



<U>CHECK</U>


       1
+
    9  9
------------

 1  0  0



            <U>S O L U T I O N</U>



Since  "A"  is the leading digit of the sum,  it is clear that  A = 1.


Next, since a two-digit number  BB  after adding the  "1"  becomes a three-digit number  ADD, 

it is clear that  BB  is  99.   Than for the sum  ADD  there is only one possibility to be  100.
</pre>

Solved.