bài 2)
`a) ( 2 1/4 - 1 1/3) . ( 2 1/3 - 1 1/4) : 143/144`
`= (9/4 - 4/3) . ( 7/3 - 5/4) : 143/144`
`= 11/12 . 13/12 : 143/144`
`= 143/144 : 143/144`
`= 1`
-----------------------------------------------
`b) (17/5 + 3/4) . ( \frac{-1}{2} + \frac{-4}{3}) : 22/5`
`= 83/20 . (-11/6) : 22/5`
`= -913/120 . 5/22`
`=-83/48`
-----------------------------------------------------
`c) 1/3 . (\frac{-9}{8}) . 12/11 : (-2 8/11)`
`= -3/8 . 12/11 : (-30/11)`
`=-9/22 . (-11/30)`
`= 3/20`
-----------------------------------------------------
`d) ( 2 1/2 + 3) : (-1/3 + 2/5)`
`= (5/2 + 3) : 1/15`
`= 11/2 : 1/15`
`= 165/2`
