Mark uses 1 pt 9 fl oz and then 2 pt 10 fl oz from a container of film
developer that holds 3 qt. How much of the developer remains?
there are 16 ounces in a pint
there are 2 pints in a quart
therefore 32 ounces per quart.
so
we start with 3*32 = 96 oz
we used 16+9 = 25 and 32+10 = 42
which is 67
so
96 - 67 = 29 oz left
which is 16 + 13 or one pint 13 oz