If an equation can be rearranged into the form \(y = mx + c\), then its graph will be a straight line. In the above: \(x + y = 3\) can be rearranged as \(y = 3 – x\) (which can be re-written as ...
Draw the graph of \(y = 3x - 1\). If you recognise this as a straight line then just choose two ‘easy’ values of \(x\), work out the corresponding values of \(y\) and plot those points.