12.[43-(6-x)]=384

              6-x=43-384:12

              6-x=11

                 x=6-11

                 x=-5

Vậy: x=-5

Ta có:\(\dfrac{201201}{202202}\)=\(\dfrac{201}{202}\);\(\dfrac{201201201}{202202202}\)=\(\dfrac{201}{202}\)

=>\(\dfrac{201}{202}\)=\(\dfrac{201}{202}\) 

=> \(\dfrac{201201}{202202}\)=\(\dfrac{201201201}{202202202}\)

Vậy: \(\dfrac{201201}{202202}\)=\(\dfrac{201201201}{202202202}\)

                                        (quá dễ)

b) \(\dfrac{3}{5}\)x - \(\dfrac{1}{3}\) = \(\dfrac{4}{3}\)

        x       = \(\dfrac{3}{5}\) : (\(\dfrac{4}{3}\) + \(\dfrac{1}{3}\))

        x       = \(\dfrac{9}{25}\)

Vậy: x = \(\dfrac{9}{25}\)

a) \(\dfrac{5}{8}\) + \(\dfrac{3}{8}\) :\(\dfrac{2}{3}\) = \(\dfrac{5}{8}\) + \(\dfrac{3}{8}\) .\(\dfrac{3}{2}\) = \(\dfrac{5}{8}\) + \(\dfrac{9}{16}\) = \(\dfrac{10}{16}\) + \(\dfrac{9}{16}\) = \(\dfrac{19}{16}\)

b) \(\dfrac{1}{72}\) .\(\dfrac{144}{23}\) + \(\dfrac{1}{46}\) = \(\dfrac{2}{23}\) + \(\dfrac{1}{46}\) = \(\dfrac{4}{46}\) + \(\dfrac{1}{46}\) = \(\dfrac{5}{46}\)