6x-3y=12
Step 1- move the 6x to the other side using the opposite operation (-6x)
-3y=12-6x
Step 2- divide everything by -3
y=-4+2x
Step 3- rearrange into the correct order (y-mx+b)
y=2x-4
Step A is wrong because the 12 wasn;t changed to the inverse or opposite operation (-12), while the others were changed.
