a) \(x-\dfrac{3}{7}=-\dfrac{7}{12}\)
\(\Rightarrow x=-\dfrac{7}{12}+\dfrac{3}{7}\)
\(\Rightarrow x=-\dfrac{49}{84}+\dfrac{36}{84}\)
\(\Rightarrow x=-\dfrac{13}{84}\)
b) \(\left(-0,12\right)\left(x-\dfrac{9}{10}\right)=-1,2\)
\(\Rightarrow x-\dfrac{9}{10}=\dfrac{-1,2}{-0,12}\)
\(\Rightarrow x-\dfrac{9}{10}=10\)
\(\Rightarrow x=10+\dfrac{9}{10}\)
\(\Rightarrow x=\dfrac{109}{10}\)