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