Answer
See the graph below.
Work Step by Step
The two spheres have the same amount, but unlike, of charge.
The two spheres have the same size and the same mass.
So, the 0-V line must be in the middle between the two spheres and it bisects the line between the two spheres' centers.
And hence, the equipotential lines must be symmetric around the 0-V line.
See the graph below.
