The following shape is not a rectangle, but a square. I know this because the length and width are the same amount of square inch(feet, what ever the square counts for on your graph.) and rectangles width are typically longer than their length. However a square shares the same length and width,
It makes the addition easier if you combine like terms like the two 1/2s and then make them all have the denominator of 12 (changing the numerators to equal it out)