Question

9+3x=+x-9??? 2x+6+x=-12

Answer 1

Basta isolar o x em ambas:

a) 9+3x = x -9 
     2x = -18
       x = -9

b) 2x+6+x = -12
     3x = -18
       x = -6

Answer 2

9+3x=x-9
3x-x=-9-9
2x=-18
x=-18/2
x=-9

2x+6+x=-12
2x+x=-12-6
3x=-18
x=-18/3
x=-6