3/7 * (4.2b - 2/3c) - 3.6(5/9)b - 0.5c

Решение: \frac{3}{7}(4.2b - \frac{2}{3}c) - 3.6(\frac{5}{9})b - 0.5c = \frac{3}{7} * 4.2b - \frac{3}{7} * \frac{2}{3}c - \frac{36}{10} * \frac{5}{9}b - 0.5c = \frac{3 * 42}{7 * 10}b - \frac{2}{7}c - \frac{4 * 5}{10}b - 0.5c = \frac{3 * 6}{10}b - \frac{2}{7}c - \frac{20}{10}b - 0.5c = \frac{18}{10}b - \frac{2}{7}c - 2b - 0.5c = 1.8b - \frac{2}{7}c - 2b - 0.5c = (1.8 - 2)b + (-\frac{2}{7} - 0.5)c = -0.2b + (-\frac{2}{7} - \frac{1}{2})c = -0.2b + (-\frac{4}{14} - \frac{7}{14})c = -0.2b - \frac{11}{14}c **Ответ:** -0.2b - 11/14 c