what is the surface area?????

The area of a triangle is found using the formula Area = 1/2 x base x height.
Base = 8
Height = 18.
The area of 1 triangle = 1/2 x 8 x 18 = 72 square units.
There are a total of 4 sides, so total area = 72 x 4 = 288 units ^2