$(12+18)-(29-3)=4$ 
There are $$29$$ students in a certain class. $$12$$ of the students have a sister and $$18$$ of the students have a brother. In this class, only Tania, Barbara, and Anna do not have any siblings. How many students from this class have both a brother and a sister? ($$2003$$ Math Kangaroo Problems, Level $$3-4$$, Question \#$$17$$) 

1. $$$$None 
2. $$1$$ 
3. $$3$$ 
4. $$4$$ 
5. $$6$$ 