Make sure you are familiar with finding the equation of a line and calculating gradient to understand equations of parallel lines. If you are working at Higher tier, make sure you are confident ...

If two lines are parallel then, they have no solution pair of linear equations is inconsistent; If two lines are coincident then, they have infinite solution and pair of linear equations is ...

Two straight lines are obtained when we plot a pair of linear equations on the graph paper ... i.e., they are parallel. The two lines are co-incident. Express y in terms of x.