Can you find sets of sloping lines that enclose a square?
How does the position of the line affect the equation of the line?
What can you say about the equations of parallel lines?
Position the lines so that they are perpendicular to each other.
What can you say about the equations of perpendicular lines?
What is the area, (in square units) of the triangle formed by the three lines whose equations are: $y-x=6$, $x-2y=3$ and $x+y=6$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.