Answer:
 The area of a rectangle is 42 units ².
Step-by-step explanation:
As the diagram is given below.
Distance Formula

As the rectangle with vertices at A (4, 3), B(11, 3),C (11, 9), and D (4, 9).
Take A (4, 3) to B(11, 3)




AB = 7 units
As take B(11, 3) to C (11, 9).




BC = 6 units
As take C (11, 9) toD (4, 9).




CD =  7 units
As take  D (4, 9) to  A (4, 3)




DA =  6 units
Thus
AB = DC= 7 units
AD = BC = 6 units
Formula
Area of rectangle = Length × Breadth 
Length = 7 units
Breadth = 6 units
Put value  in the above
Area of rectangle =  7 × 6  
                              = 42 units ²
Therefore the area of a rectangle is 42 units ².