Calculate the area of the LARGE triangle...then subtrat the two smaller triangles.
You can calculate the angles of ADE.....find the hypotenuse....you are given two sides
then you can calculate the angles FEB CDG etc
Example : 180 - AED - 90 = FEB to find the side lengths of those triangles and their areas......etc,,,
Or calculate the area AED and add the rectangle when you find the side lengths.....
I come up with the following:
the 75 degree angle between the two first chords is repeated until the endpoint is back to A
the ARC this angle encompasses is 2 * 75 = 150 degrees
Keep adding 150 degree shifts until the endpoint coincides with A:
The LCM of 150 and 360 degrees (which will bring us back to A) is 1800
1800/150 = 12 angles which will require a total of 13 chords to complete