That's an equilateral triangle (a three sided regular polygon) with a height of 7 m.
The equilateral triangle bisected along its altitude is the biggest cliche in geometry, the 30/60/90 right triangle, sides in ratio 1:√3:2.
In this story the apthem is the height, let's call it h, and we'll call the other leg w. w:h=1:√3 so w = h/√3
The area of the 30/60/90 triangle is wh/2 and the equilateral triangle is two of these so its area Δ is
Δ = wh = h²/√3
We have h = 7m
Δ = 49/√3 ≈ 28.290163190291665
We could move the radical to the numerator for a high school ready exact answer but I'll just say
Answer: 49/√3 square meters
