Question 1053695
<pre>

12+(-3)-4-(-4)    
      9-4-(-4)   <--  replaced 12+(-3) from previous step by 9
        5-(-4)   <--  replaced 9-4 from previous step by 5
        5+4      <--  replaced 5-(-4) from previous step by 5+4 
          9      <--  replaced 5+4 from previous step by 9

Edwin</pre>