Answer
See the angular position-versus-time graph below,
Work Step by Step
We know that the angular velocity is given by
$$\omega=\dfrac{\theta}{t}$$
and to find the angular position of an object from its angular velocity versus time graph, we need to find the area under the curve since
$$\theta=\omega t$$
Thus, from $t=0$ s to $t=4$ s, the area under the curve is given by
$$A_1=\theta_1=\omega_1 \Delta t_1=20\cdot 4=\bf 80\;\rm rad$$
And the area under the curve from $t=4$ s to $t=6$ s is given by
$$A_2=\theta_2=\omega_2 \Delta t_2=2\cdot 2=\bf 0\;\rm rad$$
Finally, the area under the curve from $t=6$ s to $t=8$ s is given by
$$A_3=\theta_3=\omega_3\Delta t_3=-10\cdot 2=\bf -20\;\rm rad$$
Now we can draw the angular position-versus-time graph, as we see below.