a) $$\frac{2}{7} z = 1\frac{1}{7}$$
$$\frac{2}{7} z = \frac{8}{7}$$
$$z = \frac{8}{7} : \frac{2}{7}$$
$$z = \frac{8}{7} \cdot \frac{7}{2}$$
$$z = 4$$
Ответ: $$z = 4$$