First.--Write the names of the different units to be used in addition,
placing them in a horizontal row, the largest to the left.
Next.--Write the numbers of each unit to be added, below the names of
the units, each in its proper place.
Then.--Add and place each sum below the column added.
EXAMPLE: Add 7 hours 15 minutes 30 seconds, 9 hours 30 minutes 40
seconds, and 11 hours 40 minutes 32 seconds.