a]
[tex]-2\frac{1}{2}\cdot(-\frac{27}{28})=2\frac{1}{2}\cdot\frac{27}{28}=\frac{5}{2}\cdot\frac{27}{28}= \frac{5 \cdot 27}{2 \cdot 28}= \frac{135}{56}=2\frac{23}{56}[/tex]
c]
[tex]-1\frac{1}{7}\cdot1\frac{11}{24}:\frac{3}{5}= -\frac{8}{7}\cdot\frac{35}{24}\cdot\frac{5}{3}=-\frac{1}{7}\cdot\frac{35}{3}\cdot\frac{5}{3}=-\frac{1\cdot35\cdot5}{7\cdot3\cdot3}=-\frac{105}{63}=-1\frac{42}{63}[/tex]
d]
[tex]3\frac{1}{2}-3\frac{1}{6}:(-2\frac{1}{9})=3\frac{1}{2}+3\frac{1}{6}:2\frac{1}{9}=3\frac{1}{2}+\frac{19}{6}:\frac{19}{9}=\\\\=3\frac{1}{2}+\frac{19}{6}\cdot\frac{9}{19}=3\frac{1}{2}+\frac{1}{2\cdot3}\cdot\frac{3\cdot3}{19}=3\frac{1}{2}+\frac{3}{2}=3\frac{4}{2}=3+2=5[/tex]
