6x + 4 ( 4-8 ) = 9x+21 ???

Răspuns :

6x + 4(4-8) = 9x + 21

6x +4*-4 = 9x + 21

6x  - 16 = 9x + 21

6x -9x= 21 + 16

-3x = 37

x = -37/3

6x+16-32=9x+21

6x-16=9x+21

6x-9x=21+16

-3x=37

x=-37/3