[tex]B=\frac{12}{\frac{-4}{9}}\\
B= \frac{12}{-4} *9 = -3 * 9 = -27 [/tex]
[tex] C=\frac{3-\frac{9}{2}}{\frac{6}{5}+3}\\
C=\frac{\frac{6-9}{2}}{\frac{6+15}{5}}\\
C= \frac{6-9}{2} * \frac{5}{6+15}\\
C=\frac{-3}{2} * \frac{5}{21}\\
C\frac{-15}{42}=\frac{-5}{14}[/tex]