Triangles FAD, BAF, BFD, and CED are
Segment BC is the side of the shaded square. If you know
the length of segment BC, you can find the area.
figure described in the hint is shown.
The total unshaded area is 12 units, so the unshaded area inside
12-by-12 square is 6 units. The total area of the original square
is 10 units, so the fraction of the original square which is shaded
side of the shaded square can be found from the first three hints by
subtracting AB and CD from AD.
gives the solution, .To
find the solution without the side of the shaded square, use the ratio
found in the last hint and compute