[tex]7.a)(3- \frac{1}{3}\cdot)( \frac{9}{8})^{2}= \frac{3\cdot3-1}{3}\cdot \frac{9^{2} }{8^{2} } = \frac{8}{3}\cdot \frac{ 9^{2}}{8^{2}} = \frac{3^{3}}{8}= \frac{27}{8} [/tex]
[tex]b) \frac{3}{4}: (\frac{3}{4}- \frac{1}{2})- \frac{4}{9}= \frac{3}{4}:( \frac{3}{4}- \frac{1\cdot2}{2} )- \frac{4}{9} = \frac{3}{4}\cdot\frac{4}{1}- \frac{4}{9} =3-\frac{4}{9}= \frac{27-4}{9}= \frac{23}{9} [/tex]
