Aregular triangular pyramid has a base and lateral faces that are congruent equilateral triangles. it has a lateral surface area of 57 square centimeters. what is the surface area of the regular triangular pyramid?

So hmm notice the picture below

the 3 lateral sides of the triangular pyramid, are just 3 congruent triangles

they all add up to an area of 57, thus the area of 1 is 57/3

that's just the lateral area

the surface area of the triangular pyramid, includes all, laterals plus base, or the one at the bottom

so, the surface area is, the lateral 57, plus the area of the one at the bottom