You have to assume that 1 square on the x axis = 1 unit and 1 square on the y axis = 1 unit.
To find the slope, you use the carpenter's rule of rise divided by the run. Using the point on the slanted blue line as the reference point, you get
The rise = 1 on the y axis
The run = 2 on the x axis
So the slope is 1/2 and it is positive. Pick the orange one.
