【1】You are saying that everyone should be equal, and this is what I agree with.

解答:“what”引导表语从句并在表语从句作介词with的宾语。

备注:what=the thing that引导关系分句作主句的表语.

【2】You are saying that everyone should be equal, and this is why I agree with you.

解答:“why”引导表语从句并在表语从句作原因状语。

备注:why=the reason why引导关系分句作主句的表语。

【3】You are saying that everyone should be equal, and this is where I agree.

解答:“where”引导表语从句并在表语从句作地点状语。

备注:where=the place where引导关系分句作主句的表语。