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Bài 4 :
` d, x xx 4/7 = 8/3`
`x = 8/3 : 4/7`
`x = 8/3 . 7/4 `
`x = 14/3`
Vậy ` x = 14/3`
` b, 2/5 : x = 1/3`
`x = 2/5 : 1/3`
`x = 2/5 . 3`
`x = 6/5`
Vậy ` x = 6/5`
` c ,x : 7/11 = 22`
`x = 22 xx 7/11`
`x = 154/11`
`x = 14`
Vậy ` x = 14`
Bài 5 :
` 8/7 - y xx 2/3 = 3/4`
`y xx 2/3 = 8/7 - 3/4`
` y xx 2/3 = 11/28`
` y = 11/28 : 2/3`
`y = 11/28 xx 3/2`
`y = 33/56`
Vậy ` y = 33/56`
`b, y xx 4/6 + 3/4 = 7/8`
`y xx 4/6 = 7/8 - 3/4`
`y xx 4/6 = 1/8`
`y = 1/8 : 4/6`
`y = 1/8 xx 6/4`
`y = 3/16`
Vậy ` y = 3/16`
`c, y xx 2/3 + 5/4 = 20/14`
` y xx 2/3 = 10/7 - 5/4`
`y xx 2/3 = 5/28`
`y = 5/28 : 2/3`
`y = 5/28 xx 3/2`
`y = 15/56`
Vậy ` y = 15/56`