Б. 1 целая 3/7z плюс 7/8 равно 1 целая 3/8. в.7/9x минус 5/18x плюс 1/4x равно 1/6.

Б
$1 \frac{3}{7}z+ \frac{7}{8}=1 \frac{3}{8} \\\\ \frac{10}{7}z= \frac{11}{8}- \frac{7}{8} \\\\ \frac{10}{7}z= \frac{4}{8} \\\\ z= \frac{4}{8}: \frac{10}{7}= \frac{1}{2}* \frac{7}{10} = \frac{7}{20}$

В.
$\frac{7}{9}x- \frac{5}{18}x + \frac{1}{4}x= \frac{1}{6} \\ \\ \frac{28}{36}x- \frac{10}{36}x+ \frac{9}{36}x = \frac{1}{6} \\ \\ \frac{27}{36}x= \frac{1}{6} \\\\ \frac{3}{4}x= \frac{1}{6} \\ \\ x= \frac{1}{6}: \frac{3}{4}= \frac{1}{6}* \frac{4}{3}= \frac{2}{9}$