1) \frac{42x-9 x^{2} +49}{42x}
2) \frac{1}{3x} - \frac{1}{7} = \frac{7-3x}{21x}
3) \frac{42x-9 x^{2} +49}{42x} : \frac{7-3x}{21x} = \frac{42x-9 x^{2} +49}{42x} * \frac{21x}{7-3x}
\frac{42x-9 x^{2} +49}{42x} * \frac{21x}{7-3x} = \frac{42x-9 x^{2} +49}{2(7-3x)}