Question 805785
<pre>
  9:55 PM
 -1:43
------
  8:12 PM

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Note:  If it had finished at 9:20 PM you would have 
needed to borrow 60 minutes from 9 o'clock and 
considered 9:20 PM as 8:80 PM:

 8:80 PM
-1:43
-----
 7:37 PM 

Edwin</pre>