Bài `2:`

`a,`

`( 2 xx x + 30 )/6 = ( 3 xx x + 5 )/3`

`=> ( 2 xx x + 30 )/6 = ( 2 xx 3 xx x + 5 xx 2 )/6`

`=> ( 2 xx x + 30 )/6 = ( 6 xx x + 10 )/6`

`=> 2 xx x + 30 = 6 xx x + 10`

`=> 2 xx x + 30 - 10 = 6 xx x `

`=> 2 xx x + 20 = 6 xx x`

`=> 20 = 6 xx x - 2 xx x`

`=> 20 = ( 6 - 2 ) xx x`

`=> 20 = 4 xx x`

`=> 4 xx x = 20`

`=> x = 20 : 4`

`=> x = 5`

Vậy `x = 5`

`b,`

`x xx 30% - x xx 1/5 = 4`

`=> x xx 3/10 - x xx 1/5 = 4`

`=> x xx ( 3/10 - 1/5 ) = 4`

`=> x xx ( 3/10 - 2/10 ) = 4`

`=> x xx 1/10 = 4`

`=> x = 4 : 1/10`

`=> x = 4 . 10`

`=> x = 40`

Vậy `x = 40`

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