Works on the same principle as "60 seconds = 1 minute and 60 minutes = 1 hour (or degree in this case)...
So for example: 2 degrees, 45 Minutes and 20 seconds is worked as follows:
Now, 20 seconds = 0.33 minutes (i.e. 20/60); add to 45 minutes to get 45.33 minutes..
45.33 minutes = 45.33/60 degrees = 0.7555 degrees.
Therefore, final answer is 2 + 0.7555 = 2.7555 degrees....
Hope this helps!!