$\"\"$

The area of the quadrilateral is equal to the sum of the areas of $\"\"$ and $\"\"$ .

Area of ABCD = area of $\"\"$ + area of $\"\"$ .

$\"\"$

$\"\"$ (Substitute $\"\"$ )

$\"\"$ (Simplify)

$\"\"$ (Add: $\"\"$ ) $\"\"$

The area of quadrilateral ABCD is $\"\"$ .