Answer:84.84m^2
Edit: I redid it doing the base separate and got 84.847 because Pythagorean theorem tells you the sides of the three triangles are 6.998 which is ever so slightly smaller than the base triangle.
Explanation:
This is assuming the triangles are equal. 1/2bh gives you 21.21 for the triangle with the given height and then multiplying that by four for all the sides gives you 84.84m^2. The question doesn’t specify what type of pyramid it is so again I’m assuming it’s equal. Not 100% positive hope it can help at all.