a. x+4/5-x+4=x/3-x-2/2 b.4x+3/5-6x-2/7=5x+4/3+3 c. 5x+2/6-8x-1/3=4x+2/5-5

a/3x+2/ 2-3x+1/6=5/3+2x   ( x khác  2/3)

<=> 3x + 2/ 2-3x +1/6 – 5/3 – 2x = 0

<=> 3x + 2/ 2-3x – 3/2 – 2x = 0

<=> 2 ( 3x + 2 ) – 3 ( 2 – 3x) – 4x ( 2 – 3x ) / 2 ( 2 – 3x ) = 0

<=> 6x + 4 – 6 + 9x – 8x + 12x^2 / 2 ( 2 – 3x ) = 0 

<=>  7x – 2 + 12x^2 = 0 

<=> 12x^2 + 7x – 2 = 0

<=> x = -7 cộng trừ căn bậc 7^2 – 4 . 12 . ( – 2) / 2 . 12

<=> x = -7 cộng trừ căn bậc 49 + 96 / 24

<=>  x = – 7 cộng trừ căn bậc 145 / 24 

b/4x+3/5-6x-7/2=5x+4/3+3 ( x khác 5/6 ) 

<=> 4x + 3 / 5 – 6x – 7/2 – 5x + 4 / 6 = 0

<=> 6 ( 4x + 3 ) – 21 ( 5 – 6x ) – ( 5 – 6x ) ( 5x + 4 ) / 6 ( 5 – 6x ) = 0

<=> 24x + 18 – 105 + 126x – ( 25x + 20 – 30x^2 – 24x ) / 6 ( 5 – 6x ) = 0

<=> 24x + 18 – 105 + 126x – ( x + 20 – 30x^2 ) / 6 ( 5 – 6x ) = 0

<=> 24x + 18 – 105 + 126x –  x – 20 + 30x^2  / 6 ( 5 – 6x ) = 0

<=> 149x – 107 + 30x^2 / 6 ( 5 – 6x ) = 0

<=> 149x – 107 + 30x^2 = 0

<=> x = – 149 cộng trừ căn bậc 149^2 – 4 . 30 . ( – 107 ) / 2. 30

<=> x = – 149 cộng trừ căn bậc 35041 / 60