5x + 11 = 9 - x
<=> 5x = 9 - 11 - x
<=> 5x + x = - 20
<=> 6x = - 20
=> x =\(\frac{-20}{6}\)
5.(x + 4/11 ) = x- 2/22
=> 5.x + 5. 4/11 =x - 2/22
=> 5.x + 20/11 = x- 2/22
=> 5.x - x = -2/22 - 20/11 (quy tắc chuyển vế)
=> 4.x = 21/11
=> x = 21/11 : 4
=> x= 21/44