Решение:
а) $3(x + 2) - x = 10$
$3x + 6 - x = 10$
$3x - x = 10 - 6$
$2x = 4$
$x = \frac{4}{2} = 2;$
б) $8 = 3(x - 4) - x$
$8 = 3x - 12 - x$
$-3x + x = -12 - 8$
$-2x = -20$
$x = \frac{-20}{-2} = 10;$
в) $4x + 3(x - 7) = 5$
$4x + 3x - 21 = 5$
$4x + 3x = 5 + 21$
$7x = 26$
$x = \frac{26}{7} = 3\frac{5}{7};$
г) $3(x - 1) + x = 2x$
$3x - 3 + x = 2x$
$3x + x - 2x = 3$
$2x = 3$
$x = \frac{3}{2} = 1\frac{1}{2};$
д) $5 - x = 4(x - 3)$
$5 - x = 4x - 12$
$-x - 4x = -12 - 5$
$-5x = -17$
$x = \frac{-17}{-5} = 3\frac{2}{5};$
е) $5(x + 4) + x = 6$
$5x + 20 + x = 6$
$5x + x = 6 - 20$
$6x = -14$
$x = \frac{-14}{6} = -2\frac{1}{3};$
ж) $7 - (2x + 3) = 9$
$7 - 2x - 3 = 9$
$-2x = 9 - 7 + 3$
$-2x = 5$
$x = \frac{5}{-2} = -2\frac{1}{2};$
з) $3(x - 7) - 6x = -x$
$3x - 21 - 6x = -x$
$3x - 6x + x = 21$
$-2x = 21$
$x = \frac{21}{-2} = -10\frac{1}{2};$
и) $\frac{1}{2}(x - 4) + 3x = 5$
$\frac{1}{2}x - 2 + 3x = 5$
$\frac{1}{2}x + 3x = 5 + 2$
$3\frac{1}{2}x = 7$
$x = 7 : 3\frac{1}{2} = 7 * \frac{2}{7} = 2;$
к) $2(x + \frac{3}{5}) - x = 3\frac{1}{5}$
$2x + \frac{6}{5} - x = 3\frac{1}{5}$
$2x - x = 3\frac{1}{5} - \frac{6}{5} = 2;$
л) $5x - (\frac{1}{2}x + 9) = 18$
$5x - \frac{1}{2}x - 9 = 18$
$5x - \frac{1}{2}x = 18 + 9$
$4\frac{1}{2}x = 27$
$x = 27 : 4\frac{1}{2} = 27 * \frac{2}{9} = 6;$
м) $-2(\frac{1}{3}x + 7) = -21$
$-\frac{2}{3}x - 14 = -21$
$-\frac{2}{3}x = -21 + 14$
$-\frac{2}{3}x = -7$
$x = 7 : -\frac{2}{3} = 7 * -\frac{3}{2} = \frac{21}{2} = 10\frac{1}{2}.$
Ответ:
а) $2;$
б) $10;$
в) $3\frac{5}{7};$
г) $1\frac{1}{2};$
д) $3\frac{2}{5};$
е) $-2\frac{1}{3};$
ж) $-2\frac{1}{2};$
з) $-10\frac{1}{2};$
и) $2;$
к) $2;$
л) $6;$
м) $10\frac{1}{2}.$