Extend the side that's 9.5 meters long out to the left so that you form a trapezoid on top and a rectangle underneath. The side we extended is now 5+9.5 = 14.5 meters long.
Let
A = area of the trapezoid up top
B = area of the rectangle underneath
The goal is to find A+B
The trapezoid has the parallel sides of 14.5 and 10 meters. The height of the trapezoid is 28-20 = 8 meters. So we can say
Area of trapezoid = height*(base1+base2)/2
A = h*(b1+b2)/2
A = 8*(14.5+10)/2
A = 98
The rectangle has area of B = length*width = 5*20 = 100 square meters
