a)
\frac{3}{4}+\frac{2}{3}:(-\frac{8}{12})=\frac{3}{4}+\frac{2}{3}:(-\frac{2}{3})=\frac{3}{4}+\frac{2}{3}*(-\frac{3}{2})=\frac{3}{4}-1=-\frac{1}{4}
b)
\frac{(2-\frac{1}{7})*3}{2+0,6}=\frac{(\frac{14}{7}-\frac{1}{7})*3}{2,6}=\frac{\frac{13}{7}*3}{\frac{26}{10}}=\frac{39}{7}*\frac{10}{26}=\frac{3}{7}*\frac{10}{2}=\frac{3}{7}*5=\frac{15}{7}=2\frac{1}{7}
c)
(\frac{1}{3}+\frac{2}{7}):(1-\frac{1}{9})+\frac{3}{7}=\frac{7+6}{21}:\frac{8}{9}+\frac{3}{7}=\frac{13}{21}*\frac{9}{8}+\frac{3}{7}=\frac{13}{7}*\frac{3}{8}+\frac{3}{7}=
\frac{39}{56}+\frac{24}{56}=\frac{63}{56}=\frac{7*9}{7*8}=\frac{9}{8}=1\frac{1}{8}
d)
(2*\frac{5}{6})^2-(3^2-\sqrt{1\frac{7}{9}})=(\frac{5}{3})^2-(9-\sqrt{\frac{16}{9}})=\frac{25}{9}-(9-\frac{4}{3})=\frac{25}{9}-\frac{81}{9}+\frac{12}{9}=-\frac{44}{9}=-4\frac{8}{9}
e)
[(-\frac{2}{3})^2:\frac{8}{9}]^{-1}=(\frac{4}{9}*\frac{9}{8})^{-1}=(\frac{1}{2})^{-1}=2^1=2
f)
1,6*\frac{7}{16}-\frac{2,7}{3^3}=\frac{16}{10}*\frac{7}{16}-\frac{2,7}{27}=0,7-0,1=0,6