The area of the rectangle is defined as its length multiplied by its width. This rectangle has a length of 3 ft and a width of (c + 4) ft, so its area would be [tex]3(c+4)[/tex] feet. Using the distributive property, we can simplify this to:
[tex]3c+3(4)\\
3c+12[/tex]
So the area of this particular rectangle would be 3c + 12 sq. ft