mik chỉ lm đc 1 câu thôi mong bn like cho
(13911:3849−5211:3849):(4938.511)={(13+911).4938−(5+211).4938}:(4938.511)=4938.(13−5+911−211):(4938.511)=4938.(8+711):(4938.511)=(8+711):511=19

a) A = $\frac{124}{125}+(\frac{-18}{15}+\frac{1}{125})+\frac{3}{15}$

     = $(\frac{124}{125}+\frac{1}{125})+(\frac{-18}{15}++\frac{3}{15})$

     = $\frac{124+1}{125}+\frac{-18+3}{15}$

     = 1 + (-1)

     = 0 
  

b) B = $(\frac{1}{9}-\frac{5}{17})+\frac{3}{6}+(\frac{-12}{17}+\frac{-1}{2})+\frac{5}{9}$

     = $(\frac{1}{9}+\frac{5}{9})+(\frac{-12}{17}-\frac{5}{17})+(\frac{3}{6}+\frac{-1}{2})$

     = $\frac{1+5}{9}+\frac{-12-5}{-17}+\frac{1+(-1)}{2}$

     = $\frac{2}{3}-1+0$

     = $\frac{-1}{\mathrm{3\; like\; đê}}$

3 tổ có số h/s là:
    9x3=27<hs>
         đáp số :27hs