a) $$\frac{56}{17} = 3\frac{5}{17}$$.
$$\frac{355}{27} = 13\frac{4}{27}$$.
$$\frac{15}{12} = 1\frac{3}{12} = 1\frac{1}{4}$$.
б) Дробная часть:
$$3\frac{19}{10} = 3 + \frac{19}{10} = 3 + 1\frac{9}{10} = 4\frac{9}{10}$$.
$$5\frac{38}{15} = 5 + \frac{38}{15} = 5 + 2\frac{8}{15} = 7\frac{8}{15}$$.
$$4\frac{72}{36} = 4 + \frac{72}{36} = 4 + 2 = 6$$.
$$2\frac{36}{12} = 2 + \frac{36}{12} = 2 + 3 = 5$$.
Ответ: а) $$3\frac{5}{17}, 13\frac{4}{27}, 1\frac{1}{4}$$; б) $$4\frac{9}{10}, 7\frac{8}{15}, 6, 5$$.