Решение:
\[ 18x - 18 + 9 - 12x = 24 \]
\[ 6x - 9 = 24 \]
\[ 6x = 24 + 9 \]
\[ 6x = 33 \]
\[ x = \frac{33}{6} = \frac{11}{2} = 5,5 \]
\[ 4(1,5x - 0,2) - \frac{78}{15} = 4 - (\frac{1}{6} - 1,5x) \]
\[ 6x - 0,8 - 5,2 = 4 - \frac{1}{6} + 1,5x \]
\[ 6x - 1,5x = 4 - \frac{1}{6} + 0,8 + 5,2 \]
\[ 4,5x = 10 - \frac{1}{6} \]
\[ \frac{9}{2}x = \frac{60 - 1}{6} \]
\[ \frac{9}{2}x = \frac{59}{6} \]
\[ x = \frac{59}{6} \times \frac{2}{9} = \frac{59}{3 \times 9} = \frac{59}{27} \]
Ответ: а) 5,5; б) 59/27