As what I can observe, the pathway can be formed with 2 right triangles. Thus, I'll get the area of the 2 right triangles and multiply its area by the paving cost per square meter.
Area of Right Triangle: ab / 2
a = 6 2/3 m ⇒ 20/3 m; b = 3m
Area of 1 triangle= (20/3 m * 3 m) ÷ 2 = 20 ÷ 2 = 10 m²
Area of 2 triangles = 10m² * 2 = 20 m²
Total cost = $40 * 20m² = $800
