№12. Решите уравнение: 2 a)1,7x--x-0,9x = 0,24; 3 б)0,29у +0,78у – 2,1y – 0,4y = 15,73; 6)8.(0,7x-4)-2-(0,2x-3) = -39; 5 4 г) (0,54-7,2y)---(0,76-3,8y) = 0,002. 18 19

№12.

a) \[1.7x - \frac{2}{3}x - 0.9x = 0.24\]

\[\frac{17}{10}x - \frac{2}{3}x - \frac{9}{10}x = \frac{24}{100}\]

\[\frac{51x - 20x - 27x}{30} = \frac{6}{25}\]

\[\frac{4x}{30} = \frac{6}{25}\]

\[x = \frac{6 \cdot 30}{25 \cdot 4} = \frac{180}{100} = 1.8\]

б) \[0.29y + 0.78y - 2.1y - 0.4y = 15.73\]

\[(0.29 + 0.78 - 2.1 - 0.4)y = 15.73\]

\[-1.43y = 15.73\]

\[y = \frac{15.73}{-1.43} = -11\]

в) \[8 \cdot (0.7x - 4) - 2 \cdot (0.2x - 3) = -39\]

\[5.6x - 32 - 0.4x + 6 = -39\]

\[5.2x - 26 = -39\]

\[5.2x = -13\]

\[x = \frac{-13}{5.2} = -2.5\]

г) \(\frac{5}{18} \cdot (0.54 - 7.2y) - \frac{4}{19} \cdot (0.76 - 3.8y) = 0.002\)

\[\frac{5}{18} \cdot (0.54 - 7.2y) - \frac{4}{19} \cdot (0.76 - 3.8y) = 0.002\]

\[\frac{5 \cdot 0.54}{18} - \frac{5 \cdot 7.2y}{18} - \frac{4 \cdot 0.76}{19} + \frac{4 \cdot 3.8y}{19} = 0.002\]

\[\frac{2.7}{18} - \frac{36y}{18} - \frac{3.04}{19} + \frac{15.2y}{19} = 0.002\]

\[0.15 - 2y - 0.16 + 0.8y = 0.002\]

\[-1.2y - 0.01 = 0.002\]

\[-1.2y = 0.012\]

\[y = \frac{0.012}{-1.2} = -0.01\]

Ответ: a) x = 1.8; б) y = -11; в) x = -2.5; г) y = -0.01.