Let $$\triangle$$ABC and $$\triangle$$ABD be on the same base AB and between the same parallels AB and CD.Then the relation between areas of $$\triangle$$ABC and $$\triangle$$ABD will be:

As per the information given in the question, the above diagram can be formed.

Area of a triangle = $$\frac{1}{2}\times\ base\times\ height$$

As we know from the question that both of the triangles are on the same base. It means that the value of both bases will be equal.

From the diagram, we can say that both of the triangles are having same heights.

When the height and base of both triangles are the same. Then their areas will also be the same.

Hence Area $$(\triangle ABC)$$ = Area $$(\triangle ABD)$$