Mmmmmm.......this is an interesting one !!!!
Maybe easier ways to do this....but......
Perpendicular to AB.....draw IJ through E so that I is a lies on AB and J lies on DC
This divides the gray area on the bottom into 3 areas....
Triangle AIE, Triangle HEJ and Quadrilateral IJCB
We can find the area of Tiriangle AIE as follows
AE = AB = 12
Angle IAE = 30
Angle AIE = 90
So IE = 6 and AI = 6sqrt(3)
So...the area of Triangle AIE = (1/2)(6)(6sqrt(3)) = 18sqrt (3)
So....IB = 12 - AI = 12 - 6qrt(3)
So....the area of Quadrilateral IJBC = BC * IB = 18 * [ 12 - 6sqrt(3) ] = 216 - 108 sqrt (3)
And we can find the area of Triangle HEJ as follows
Angle HJE = 90
Angle JHE = 60
EJ = BC - IE = 18 - 6 = 12
And HJ is opposite the 30 ° angle in Triangle HEJ = 12 / sqrt (3) = 4sqrt (3)
So...the area of triangle HEJ = (1/2) (12)(4sqrt(3) ) = 24sqrt(3)
So...the "bottom" Grey Area is the sum of the areas in red = 216 - 66sqrt(3) units^2
So....the "white" area = Area of Rectangle ABCD - bottom Grey Area =
18 * 12 - [ 216 - 66sqrt(3) ] =
216 - 216 + 66sqrt(3) =
66sqrt(3) units^2
And the "top" Grey Area is just the area of Rectangle AEFG - white area =
Area of Rectangle ABCD - white area =
216 - 66sqrt (3) units^2
So.....the shaded area is just the bottom grey area + top grey area
[ 216 - 66sqrt (3) ] + [ 216 - 66sqrt (3) ] =
[432 - 132sqrt(3) ] units^2