My drawing is not quite to scale, because GCDE doesn't quite
look like a rhombus.
I labeled two more points than the drawing on the site, H and I.
Area of rhombus GCDE is half the product of the diagonals.
Area of triangle EFG is half the base times height
Now all we need is the area of trapezoid ABCG.
We must find CG.
The diagonals of a rhombus are perpendicular, and therefore triangle CIG
is a right triangle. GI = DI = 7, and IC = 4, so
The area of a trapezoid is the average base times the height:
The average base of trapezoid ABCG is
The height of trapezoid is 6, so the area of trapezoid ABCG is
So we add the three areas together:
Area of trapezoid ABCG =
Area of rhombus GCDE = 56
Area of triangle EFG = 100
Answer = 
Area of rhombus GCDE is half the product of the diagonals.
Area of triangle EFG is half the base times height
Now all we need is the area of trapezoid ABCG.
We must find CG.
The diagonals of a rhombus are perpendicular, and therefore triangle CIG
is a right triangle. GI = DI = 7, and IC = 4, so
The area of a trapezoid is the average base times the height:
The average base of trapezoid ABCG is
The height of trapezoid is 6, so the area of trapezoid ABCG is
So we add the three areas together:
Area of trapezoid ABCG =
Area of rhombus GCDE = 56
Area of triangle EFG = 100
Answer =
cm2
That's approximately 222.2 cm2
Edwin