8 qt/min=___gal/h

Start out with this fraction

 8 qt
-------
 1 min

Now we need to cancel away the "qt" in the top.
We use the fact that 4 qt = 1 gal, to create
a fraction which equals 1 to multiply that
by, which has "qt" on the bottom to cancel 
away the "qt" in the top.

Such a fraction is

 1 gal
-------
 4 qt

so we multiply by that:

  8 qt      1 gal
------- × --------
 1 min      4 qt

And then the "qt"'s cancel out:

    1
  8 qt     1 gal
------- × --------
 1 min      4 qt
              1

Next we need to create another 
fraction that equals 1 to 
cancel away the "min" in the 
bottom of the first fraction.
We know that 60 min = 1 h, so 
we create the fraction 

 60 min
--------
  1 h

to multiply by. Notice we
put "min" in the top to
cancel away the "min" in
the bottom in the first
fraction. So now we have:

    1
  8 qt     1 gal     60 min 
------- × -------- × --------
 1 min     4 qt       1 h
             1


Now the "min"'s cancel out
like so

    1
  8 qt     1 gal     60 min 
------- × -------- × --------
 1 min     4 qt       1 h
             1

Now all the units have canceled
except "gal" in the top and "h"
in the bottom, which are the 
units we want, so we have

  8×60 gal
-----------
   4 h

Now we can cancel the 4 into the 8 and get 2

  2
  8×60 gal
------------
   4 h
   1


So we end up with

 2×60 gal
----------
   1 h

or 

120 gal/h

Edwin