Resistance R is given by the equation R = V/I. The slope m of the graph is also equal to m = V/I. The higher the slope of the graph, the higher the resistance R. Another way of looking at it would be, that the same current I in the graph (1) and (2), requires a higher voltage in the graph(2) than in graph(1). This means the resistance must be greater in the graph(2).
There is an simple explaination to understand the resistance through a graph. THE HIGHER THE SLOPE OF THE LINE, THE LOWER THE RESISTANCE OF THE RESISTOR.
Remember that and you can do all of the related exercises.
