39. Решите уравнение: 1) 0,8 − (1,5x − 2) = 0,8 + 4,5x; 2) 0,6x − 5(0,9x + 0,2) = 0,5(x − 1) − 0,8; 3) 1/7(7/9 y + 7) − 3/4(2/9 y + 1 7/9) = 1/12; 4) 5/27(5,4 − 8,1y) = 0,03 + 1/4(6,8 − 3,4y).

1. Раскроем скобки: $0,8-1,5x+2=0,8+4,5x$. Тогда $6x=2$, поэтому $x=\backslash (\backslash frac\{1\}\{3\}\backslash )$.
2. $-3,9x-1=0,5x-1,3$; $-4,4x=-0,3$; $x=\backslash (\backslash frac\{3\}\{44\}\backslash )$.
3. $\backslash (\backslash frac\{y\}\{9\}\backslash )+1-\backslash (\backslash left\backslash )\backslash (\backslash frac\{y\}\{6\}+\backslash frac\{4\}\{3\}\backslash right\backslash )=\backslash (\backslash frac\{1\}\{12\}\backslash )$; $-\backslash (\backslash frac\{y\}\{18\}\backslash )-\backslash (\backslash frac\{1\}\{3\}\backslash )=\backslash (\backslash frac\{1\}\{12\}\backslash )$; $y=-\backslash (\backslash frac\{15\}\{2\}\backslash )$.
4. $1-1,5y=1,73-0,85y$; $-0,65y=0,73$; $y=-\backslash (\backslash frac\{73\}\{65\}\backslash )$.

Ответ: 1) x=1/3; 2) x=3/44; 3) y=−15/2; 4) y=−73/65.