First, you want to even out each side.
[tex]11 = 12 - q [/tex]
You need to inverse -q to +q and add to both sides to get
[tex]11 + q = 12[/tex]
Now you need to do the oppisite of add to 11 which is subtract it from both sides.
[tex]q = 12 - 11[/tex]
or
[tex]q = 1[/tex]
