There is no “unique” answer to this problem, and, moreover it can be
approached by different ways (current sources or voltage sources).
The equation of the line on figure 5.5-11 is i (mA) = 20*V/3 + 20
Starting from this equation we can find a circuit or we can write
V = 3*i/20 – 3
This is thus two sources of voltage, one dependent and the other
independent.
One circuit could be (I is in mA):
The resistor R could be of any value here, as the dependent voltage
source is directly linked to the i.