Answer:
The answer is 54 units squared
Explanation:
This is because this triangle is made up of two triangles. The smaller one is an isosceles triangle, meaning all sides are the same length. Sense all sides are the same length each side = 6 units squared. You subtract 6 from 18 to get the length of the other triangles side.
From there you multiply each side as if it were a square, then divide both answers by two (because two triangles make up a square). Add them up and then Ta-daa! 54!