The shaded area is the difference of the areas of the outer square and the inner square. In turn, those areas are the square of the edge dimension of the square. So, the shaded area is the difference of squares:
area = (2x +3)² -(y -3)²
The difference of squares is a "special product" in that it has a factored form that is worth remembering.
<span>77.5% can also be written as 77.5/100, but if you're the mathematical notation police, people don't like decimals on a fraction, sooo, an equivalent form is: </span>
