Выделим целую часть:
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$$а) \frac{45}{13} = 3\frac{6}{13}$$
$$\frac{243}{45} = 5\frac{18}{45} = 5\frac{2}{5}$$
$$\frac{126}{7} = 18$$
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$$б) 4\frac{8}{7} = 4 + \frac{8}{7} = 4 + 1\frac{1}{7} = 5\frac{1}{7}$$
$$6\frac{15}{4} = 6 + \frac{15}{4} = 6 + 3\frac{3}{4} = 9\frac{3}{4}$$
$$3\frac{29}{12} = 3 + \frac{29}{12} = 3 + 2\frac{5}{12} = 5\frac{5}{12}$$
$$5\frac{21}{7} = 5 + \frac{21}{7} = 5 + 3 = 8$$
Ответ: а) $$3\frac{6}{13}$$, $$5\frac{2}{5}$$, 18; б) $$5\frac{1}{7}$$, $$9\frac{3}{4}$$, $$5\frac{5}{12}$$, 8.