The area of a triangle is given by the product of its base and the height relative to that base.
Since theses triangles have the same base b and same height h, they have the same area.
Part B:
The area of a rectangle or parallelogram is given by the product of base and height. Since these figures have the same base and height, they have the same area.
Part C:
These figures have different shapes, so we can't affirm that they have thesame area.