а) 3 = \(\frac{3 \cdot 7}{7} = \frac{21}{7}\), 4 = \(\frac{4 \cdot 7}{7} = \frac{28}{7}\), 7 = \(\frac{7 \cdot 7}{7} = \frac{49}{7}\)
б) 9 = \(\frac{9 \cdot 6}{6} = \frac{54}{6}\), 12 = \(\frac{12 \cdot 6}{6} = \frac{72}{6}\), 125 = \(\frac{125 \cdot 6}{6} = \frac{750}{6}\)