Your drawing for problem 19 seems great! Now, to find the area of the hexagon you might not need to use the formula for area of an equilateral triangle. Hint: try splitting the hexagon into small triangles.

For problem 20, extend the sides of the equiangular hexagon. You'll get a drawing similar to the one you used for problem 19. What can you say about the small triangles in the corners of this new drawing?

The diagram on 21 is showing just a portion of a huge floor covered with square tiles. The question is asking you to find other regular polygons that could also be used as tiles for a floor. Note that a shape works fine as a tile if you can arrange them together and have no gaps or overlaps between the tiles.

On 22 we want you to look at the degree measure of the exterior angles of regular polygons and tell us how many of them have integer angle measures. For example, the exterior angle in a regular quadrilateral (a square) is 90 degrees, so it is an integer angle measure, but the exterior angle in a regular heptagon is approximately $51.43$ degrees, which is not an integer angle measure.