C is the correct answer. An equilateral triangle is a type of triangle.
What you would do is multiply 72 and 3 so it says three times so you multiply 72 three times so this would equal 638
The answer to this problem would be 12. If you need to show work just comment.
Surface area is:
6*8=48
12*10=120
8*12=96
6*12=72
48+72+120+96 = 336
The surface area is 336 square km
