Bài 3: Tính: a, -11/6 - 5/4 + 7/8 b, -7/11 - 3 13/-8 - 7/12 - (-15)/4 Giúp mình với. Mình cảm ơn nhiều

$ a) \dfrac{-11}{6}-\dfrac{5}{4}+\dfrac{7}{8} $

$ =\dfrac{-44}{24}-\dfrac{30}{24}+\dfrac{21}{24} $

$ =\dfrac{-53}{24} $ 

$ b) \dfrac{-7}{11}-3\dfrac{13}{-8} - \dfrac{7}{12} - \dfrac{-15}{4} $ 

$ =\dfrac{-7}{11}-(-3)\dfrac{13}{8} - \dfrac{7}{12}+\dfrac{15}{4} $ 

$ = \dfrac{-7}{11}+3\dfrac{13}{8} - \dfrac{7}{12}+\dfrac{15}{4} $  

$ = \dfrac{-7}{11}+\dfrac{37}{8} - \dfrac{7}{12}+\dfrac{15}{4} $ 

$ = \dfrac{-168}{264}+\dfrac{1221}{264} - \dfrac{154}{264}+\dfrac{990}{264}=\dfrac{1889}{264} $