Explanation:
well, look at it for a second and focus.
what do you see ?
I see a square, where 4 quarter-circles at the corners are removed.
4 quarter-circles = 1 full circle.
so, we need to calculate the area of the square and subtract the area of the circle. that's it.
area of the square :
6 × 6 = 36 m²
area of the circle :
pi × r²
r is the radius, which is half of the diameter. the diameter is 6 m (2 quarter-circles connected with each other).
so, the radius is 3 m.
and we get
pi × 3² = 9pi m² = 28.27433388... m²
the shaded area is then
36 - 28.27433388... = 7.725666118... m² ≈ 7.73 m²