Because the area of a trapezoid is A= ((a+b)/2)h, where a is the length of the top, b is the length of the base, and h is the height, you plug that in to find your answer.
This trapezoid is sideways, but the top of it is 7m (which is a) and the base is 10 m (which is b), add a and b to get 17, A = ((17)/2)h
Now divide by 2 to get A = (8.5)h
Because the height is 9, A = (8.5)9 = 76.5
The area of the trapezoid alone is 76.5m