3x-9y=12; 27x+9y=18 are these lines perpendicular or parellel or neither

First simplify to standard form: y=x/3 - 4/3 y=x/9 + 3 look at the slope: 1/3 and 1/9 If they are reciprocals, perpendicular if they are equal, parallel Here they are neither perpendicular nor parallel.