$\"\"$

Observe the drawing, it consist of two rectangular figures and one is small and other one is big.

The length of small or inner rectangular is a and it $\"\"$ s width is b.

The small or inner rectangular is shaded by blue.

The area of a small or inner rectangle or area of the blue section is $\"\"$ .

The length of outer or big rectangular is $\"\"$ .

The width of outer or big rectangular is $\"\"$ .

The area of outer or big rectangular is $\"\"$ . $\"\"$

The area of yellow region is $\"\"$ .

$\"\"$

Rewrite as the sum of two products.

$\"\"$

Apply distributive property: $\"\"$ .

$\"\"$

Combine like terms.

$\"\"$

Apply distributive property: $\"\"$ .

$\"\"$ . $\"\"$

(a)The area of the blue section is $\"\"$ , (b)The area of outer or big rectangular is $\"\"$ and (c)The area of yellow region is $\"\"$ .