Another easy way to do this is: break it up into two sections. Break it into a triangle and a rectangle.
The triangle would have the dimensions: 20, 6, and 25.
To find the area take A x B x 1/2 = Area 20 x 6 = 120 1/2 x 120 = 60
Then, the dimensions of the rectangle would be: 30 x 20.
30 x 20 = 600 Then, 600 + 60 = 660 There's your answer!