We can divide this figure into triangle and trapezoid.
Area of a trapezoid = (1/2)*(base1 +base2)*height = (1/2)(11.75+18)*6.12 = 91.035
Area of a triangle = (1/2)*base*height=(1/2)*12*13.42 = 80.52
Area of the whole figure = 91.035 + 80.52 = 171.555