Answer
See the detailed answer below.
Work Step by Step
$$\color{blue}{\bf [a]}$$
In this situation, your thump will be pointing out of the page which is in the opposite direction of the electric flux.
So, the electric flux here is $\bf negative$.
$$\color{blue}{\bf [b]}$$
In this situation, your thump will be pointing to the left which is in the same direction of the electric flux.
So, the electric flux here is $\bf positive$.