\(\dfrac{x}{-12}\) =\(\dfrac{3}{x}\)

x.x=-12.3

x²=-36

x²=\(\pm\)6

x+\(\dfrac{1}{3}\) =\(\dfrac{2}{6}\)

x= \(\dfrac{2}{6}\) - \(\dfrac{1}{3}\) 

x=0

B =\(\dfrac{12}{13}\) + 7 -8+\(\dfrac{1}{13}\)

B =(\(\dfrac{12}{13}\)+\(\dfrac{1}{13}\))+(7-8)

B =(-1)+1

B =0

A =\(\dfrac{1}{5}\) + ( \(\dfrac{-1}{3}\)+\(\dfrac{9}{5}\) ) +\(\dfrac{-7}{6}\) 

A =\(\dfrac{1}{5}\) + \(\dfrac{22}{15}\) +\(\dfrac{-7}{6}\) 

A =\(\dfrac{1}{2}\)