a)
1,75+0,5*(\frac{2}{3})^{-1}=1\frac{3}{4}+\frac{1}{2}*\frac{3}{2}=
=1\frac{3}{4}+\frac{3}{4}=1\frac{6}{4}=2\frac{2}{4}=2\frac{1}{2}
b)
\frac{1}{12}-3*(\frac{2}{3})^2=\frac{1}{12}-3*\frac{4}{9}=
=\frac{1}{12}-\frac{4}{3}=\frac{1}{12}-\frac{16}{12}=-\frac{15}{12}=-1\frac{3}{12}=-1\frac{1}{4}