Answer: 318 km²
Let's find the areas of the triangles
Formula: base x height / 2
9 x 6 = 54
54/2 = 27
Multiply by 2 since there are two triangles (I know, we already got the areas from 9 x 6)
27 x 2 = 54
Now let's try to find the areas of all the rectangular sides
Formula: length x width
9 x 11 = 99
8 x 11 = 88
7 x 11 = 77
99 + 88 + 77 = 264
Add up all the areas
264 + 54 = 318