Explanation:
Area of a triangle = 1/2 base x height
Area of a rectangle = length x breadth
The triangle has 4km and 8km
1/2 x 8 x 4 = 32÷ 2 = 16km². area of a triangle
7km x 9km = 63 km²
The surface area is basically everything joined together making it
area of a triangle x area of a rectangle = 16km² x 63km² = 1,008km².