Answer:
28.5 km
Explanation:
2x6 eliminates the left rectangle
6x2 eliminates the tall triangle
1/2 base(height) is the formula for the area of a triangle
so following along the top we have 8 km, 11 - 8 is 3
the length above the triangle is 3 and the total length of the height is 6
so we are left with (2×6)+(6×2)+(1/2×9)=28.5