By what rule is ∆KAP ≅ ∆AKR?

Hello! First off, start with the base. 6m square is 6 x 6 = 36 square meters.

Next, you should find the area of one triangle:
1/2bh
1/2(6)(9)
1/2(54)
27 square meters.

Since there are 4 triangles, multiply this by 4. 27 * 4 = 108 square meters.

36 + 108 = 144 square meters for the net of a square pyramid.

Hope this helps! Cheerio, and good luck.