a) $$ \frac{16,8}{4,8} = \frac{168}{48} = \frac{84}{24} = \frac{42}{12} = \frac{21}{6} = \frac{7}{2} = 3,5 $$.
б) $$ \frac{11}{3\frac{1}{5}} = \frac{11}{\frac{16}{5}} = 11 \cdot \frac{5}{16} = \frac{55}{16} = 3\frac{7}{16} $$.
Ответ: а) 3,5; б) $$3\frac{7}{16}$$