Linear graphs
When drawing linear graphs by hand arrange a simple scale to use most of the graph paper (a small graph will be less accurate but don't make the scale complicated to work out) and draw the line as close to as many points as possible without distorting the straight line.
Adding or subtracting a number raises or lowers the graph line but does not change the gradient (slope)
When X is multiplied by a number then the gradient of the linear graph line is altered