`b)`
`14 . |-5| + (-4) . (-5) + |-40| : (-5)`
` = 14 . 5 + 20 + 40 : (-5)`
`= 70 + 20 - 8`
` = 82`
`c)`
`(1/2 - 4/5) . (-20) : 2/5`
` = (-3)/10 . (-20) . 5/2`
` = 6 . 5/2`
` = 15`
`d)`
`136/7 : (5/7- 1/3) + 136/7 : (15/7 - 4/3)`
`= 136/7 : 8/21 + 136/7 : 17/21`
` = 136/7 . 21/8 + 136/7 . 21/17`
` = 136/7 . (21/8 + 21/17)`
` = 136/7 . 525/136`
` = 75`
Bài `2:`
`a)`
` 13/15 . x - 4/3 = 2/5`
`=> 13/15 x = 2/5 + 4/3`
`=> 13/15 x = 26/15`
`=> x = 26/15 : 13/15`
`=> x = 2`
Vậy `x=2`
`b)`
`(9/2 - 3x) : 5/3 = 2 3/5`
`=> (9/2 - 3x) : 5/3 = 13/5`
`=> 9/2 - 3x = 13/5 . 5/3`
`=> 9/2 - 3x = 13/3`
`=> 3x = 9/2 - 13/3`
`=> 3x = 1/6`
`=> x = 1/6 : 3`
`=> x = 1/18`
Vậy `x=1/18`
`c)`
`80% . x + 2/3 x = 286`
`=> x (80% + 2/3) = 286`
`=> x . 22/15 = 286`
`=> x = 195`
Vậy `x=195`