195. Найдите значение выражения:

1) $$0,6(4y – 18) – 0,4(5 – 7у)$$ при $$y = 2\frac{4}{13}$$.
$$0,6(4y – 18) – 0,4(5 – 7у) = 2,4y - 10,8 - 2 + 2,8y = 5,2y - 12,8$$.
$$y = 2\frac{4}{13} = \frac{30}{13}$$.
$$5,2(\frac{30}{13}) - 12,8 = \frac{52}{10} \cdot \frac{30}{13} - 12,8 = \frac{4}{10} \cdot 30 - 12,8 = 12 - 12,8 = -0,8$$.
2) $$5\frac{1}{4}(12-c)+3\frac{1}{4}(-c-8)$$ при $$c = -0,4$$.
$$5\frac{1}{4}(12-c)+3\frac{1}{4}(-c-8) = \frac{21}{4}(12-c) + \frac{13}{4}(-c-8) = \frac{252}{4} - \frac{21}{4}c - \frac{13}{4}c - \frac{104}{4} = 63 - \frac{21}{4}c - \frac{13}{4}c - 26 = 37 - \frac{34}{4}c = 37 - \frac{17}{2}c$$.
При $$c = -0,4$$: $$37 - \frac{17}{2}(-0,4) = 37 + \frac{17}{2}(0,4) = 37 + 17(0,2) = 37 + 3,4 = 40,4$$.