The bulletin board is 6 ft wide and 4 ft tall. the border is 3 inches wide. what are the dimensions inside the border?

3 inches is just 3/12 or 1/4 foot
the border minuses area
so
we have
the area=legnth times wdtih
the inside length and width are 
length-2border and width-2border
because the border is on both sides

so
6-2 times 1/4=6-0.5=5.5
4-2 times 1/4=4-0.5=3.5
so the demotions inside the border are 5.5ft and 3.5ft
and the area is 19.25 square feet

9/12 is the answer because 3/4 times 3 each is 9/12