Hello,
Looking at the figure correctly, we notice that it is formed of a trapezium and a triangle.
We must therefore calculate the area of each igure.
Area of the trapeze = [(11,75 + 18) * 6,12] / 2 = 91,035 in²
Area of the triange = (12 * 13,42) / 2 = 80,52 in²
The area of the figure is therefore:
91,035 in² + 80,52 in² = 171,555 in²
Bye ;)