Could I get assistance please?

Please explain this information for me--> 

Question 7 The figure shows four pairs of charged particles. For each pair, let  V = 0 at infinity and consider  V net at points on the x axis.

Your answer is incorrect.  Try again.     For which pairs is there a point at which Vnet = 0 between the particles? (1) (2) (3) (4) None       SHOW HINT

Your answer is incorrect.  Try again.     For which pairs is there a point at which Vnet = 0 to the right of the particles? (1) (2) (3) (4) None       SHOW HINT

Your answer is correct.     At such a point is  due to the particles equal to zero? Yes No

Your answer is correct.     For each pair, are there off-axis points (other than at infinity) where Vnet = 0? Mark the pairs where this is true. (1) (2) (3) (4) None of the pairs exhibit this quality.

Unsure about this. It is similar to last weeks question. I don't know what is being asked when I read it. 

A spherical conducting shell has a charge of -37 μC on its outer surface and a charged particle in its hollow. If the net charge on the shell is -31 μC, what is the charge (a) on the inner surface of the shell and (b) of the particle?

(a)

Number

Units

° (degrees) This answer has no units m kg s m/s m/s^2 N J W N/m A V μC N/C C/m C/m^2 C/m^3 N·m^2/C

(b)

Number

Units

° (degrees) This answer has no units m kg s m/s m/s^2 N J W N/m A V μC N/C C/m C/m^2 C/m^3 N·m^2/C