In how many ways can 21 be expressed as the sum of 3 prime numbers?

321

Step-by-step explanation:

I think by using a prime factor tree

rounding to the nearest thousandth would be 452,000

a net is a diagram that shows a “flattened” view of a solid. in a net, each face and base is shown with all of its dimensions. a net can also serve as a pattern to build a three-dimensional solid.

a pyramid is a three-dimensional object with a base that is a polygon and triangular faces that meet at one vertex.

" the net of a triangular pyramid consists of four triangles. the base here we are given of the pyramid is a equilateral   triangle, and the lateral faces are also triangles "