Well, what I would do [not sure if it's the correct way], is use the white area as a sector of a circle. The top right of the box is the center of the circle, so the radius is 6.
Then, by the white portion being one quarter of the circle (90° out of 360°), I could calculate the that pink shaded region = the total square (6×6) minus the white sector.
So area (A) of white sector (s): A(s) = 1/4×pi×r^2

36 - 28.27 = 7.73
250 cm because area equals LxW and 25x10=250
16 cm.
This is because one side of the hexagon is half of one side of the square. Therefore, you multiply 8 by 2. 8x2 = 16
Equilateral because all sides are equal