7. Tìm x a) 2/3 . x = 2/7 b) x . 3/5 = 2/5 c) x : 8/13 = 13/7 d) 3/2 : x = 7/4

`a ) 2/3 . x = 2/7 `

`⇒ 2x = 2/7 . 3`

`⇒ 2x = 6/7`

`⇒ x = 3/7`

`b ) x . 3/5 = 2/5`

`⇒ 3x = 2/5 . 5`

`⇒ 3x = 10/5`

`⇒ x = 10/15 = 2/3`

`c ) x : 8/13 = 13/7`

`⇒ x/8 = 13 . 13/7`

`⇒ x/8 = 169/7`

`⇒ x = 8 . 169/7`

`⇒ x = 1352/7`

`d ) 3/2 : x = 7/4`

`⇒ 3/2 = 7/4 x`

`⇒ 4 . 3/2 = 7x`

`⇒ 6 = 7x`

`⇒ x = 6/7`