The first problem is that according to the triangle area formula, the bottom× height×1/2, we can get that the areas of triangles ABC, ACD and ADH are all equal to 3*4* 1/2=6 square centimeters, so the area of triangle ABC is 3*6= 18 square centimeters.

The second problem is that e is the midpoint of BH, so the area of triangle AEH is the area of triangle ABC, that is, 18/2=9 square centimeters.

I hope it helps you!