Please specify the class you are taking.  Students from all classes post here and it could get confusing about which class the question came from.

In any case, it appears that this is about Math Challenge I-C Winter 2023-24 class.  Problem 5.27 has a bunch of isosceles right triangles  (45-45-90) in the diagram.  As a hint, what are the lengths of $BE$ and $EC$?

In 5.30, a regular hexagon can be divided into six equilateral triangles.  A dodecagon is a $12$-sided polygon. To calculate the area, you may want to connect its vertices with its center.