area of trapezoid = (1/2)(B + b)h
where B = length of one base; b = length of the other base; h = height
You have
b = 12 ft (the upper base)
B = 8.7 ft + 12 ft = 20.7 ft (the lower base)
Now we need the height, h. The triangle has a right angle and a 30-deg angle, so the third angle must measure 60 deg. It is a 30-60-90 triangle. In a 30-60-90 triangle, the hypotenuse is trwice the length of the shourt leg. The height of the trapezoid is the short leg of the triangle.
h = (10 ft) /2 = 5 ft
The height of the trapezoid is 5 ft.
area of trapezoid = (1/2)(20.7 + 12)(5) ft^2
area = 81.75 ft^2
Answer: 81.75