4) $$4 = \frac{4 \cdot 5}{5} = \frac{20}{5}$$
$$6 = \frac{6 \cdot 5}{5} = \frac{30}{5}$$
$$18 = \frac{18 \cdot 5}{5} = \frac{90}{5}$$
$$20 = \frac{20 \cdot 5}{5} = \frac{100}{5}$$
$$31 = \frac{31 \cdot 5}{5} = \frac{155}{5}$$
$$71 = \frac{71 \cdot 5}{5} = \frac{355}{5}$$
Ответ: $$\frac{20}{5}; \frac{30}{5}; \frac{90}{5}; \frac{100}{5}; \frac{155}{5}; \frac{355}{5}$$