See attached image.
I broke it up into 4 different shapes, 3 triangles and a square.
Area for a triangle is 1/2 x base x height:
Triangle 1: 1/2 x 4 x 3 = 6
Triangle 2: 1/2 x 6 x 3 = 9
Triangle 3: 1/2 x 1 x 6 = 3
Area of square = S^2 = 6^2 = 36
Total area = 36 + 6 + 9+3 = 54 square units