a/x:12/13=-26/27
=>x=$\frac{-26}{27}$. $\frac{12}{13}$
=>x=$\frac{-8}{9}$
Vậy x=$\frac{-8}{9}$
b/(1/3)^2x-1 -(1/3)^2=-2/27
=>$\frac{1}{9}$.(x-1-1)=$\frac{-2}{7}$
=>$\frac{1}{9}$.(x-2)=$\frac{-2}{7}$
=>x-2=$\frac{-2}{3}$
=>x=$\frac{4}{3}$
Vậy x=$\frac{4}{3}$