White shirts $$=8$$  Total shirts $$=4+6+8=18$$  Fraction of shirts that are white $$=\frac{8}{18}=\frac{4}{9}$$ 
Nathan has $$4$$ red shirts, $$6$$ yellow shirts and $$8$$ white shirts. What fraction of his shirts are white? Give your answer in its simplest form. 
(1) $$\frac{8}{18}$$ 
(2) $$\frac{3}{9}$$ 
(3) $$\frac{4}{9}$$ 
(4) $$\frac{4}{5}$$ 