Помогите , пожалуйста

а) $13,8:3\frac{5}{6}*3\frac{1}{5}=\frac{138}{10} :\frac{23}{6} * \frac{16}{5} = \frac{138}{10}*\frac{6}{23} * \frac{16}{5} =11,52$

б) $(18\frac{1}{4} -17\frac{5}{6} )*8,4+6,5=\frac{5}{12} *8,4+6,5=3,5+6,5=10$

в)z-\frac{4}{9} z=\frac{9}{2} =>18z-8z=81=>10z=81=>z=8,1" alt="z-\frac{4}{9} z=4,5=>z-\frac{4}{9} z=\frac{9}{2} =>18z-8z=81=>10z=81=>z=8,1" align="absmiddle" class="latex-formula">