Solve them both for y and look at their respective coefficients of x.
These coefficients are the slopes of the lines. 

1. If the are the same, the lines are parallel.
2. If they are not parallel, then find the reciprocal of one of those
   coefficients of x, then change the sign.  If that is the same as the 
   other coefficient of x, then they are perpendicular.

If neither, then neither!

Solve the first for y:



Add -3x to both sides:





  

The coefficient of  is 

Solve the second for y:



Add +x to both sides:





  

Now we must multiply both sides by 



                2





The coefficient of  is 

------

So the two coefficients are  and 

They certainly are not the same, so they are not parallel.

So let's find the reciprocal of the  which is
 which equals  and then change the sign to 
.

We notice that we get the other.  So therefore they are perpendicular.

Edwin