[tex]\displaystyle\\
a=3(2^3\cdot2^2:2^3-2012)^0-125^3 :625^2=\\\\
=3\cdot1-(5^3)^3:(5^4)^2=3-5^9:5^8=3-5^{9-8}=3-5=-2\\
b=(72^{r+1}:6^{2r}):2^{r+2}=\frac{\dfrac{72^{r+1}}{6^{2r}} }{2^{r+2}}=
\dfrac{72^{r+1}}{6^{2r}\cdot2^{r+2}}=\dfrac{(36\cdot2)^{r+1}}{6^{2r}\cdot 2^{r+2}}=\\
=\frac{(6^2\cdot2)^{r+1}}{6^{2r}\cdot2^{r+2}}=\frac{(6^2)^{r+1}\cdot2^{r+1}}{6^{2r}\cdot 2^{r+2}}=\frac{6^{2r+2}\cdot2^{r+1}}{6^{2r}\cdot 2^{r+2}}=\\
=6^{2r+2-2r} \cdot2^{r+1-(r+2)}=6^2\cdot 2^{r+1-r-2}=36\cdot2^{-1}=36:2=18[/tex]
[tex]\displaystyle\\
\frac{3x+2}{12}=\frac{a}{b}\\\\
\frac{3x+2}{12}=\frac{-2}{18}\\\\
18(3x+2)=-2\cdot 12\\\\
54x+36=-24\\\\
54x = -24-36\\\\
54x=-60\\\\
x= \frac{-60}{54}=\boxed{\bf -\frac{10}{9}} [/tex]
