Answer: skeletal equation : 
The products are sodium nitrate and barium sulphate.
balanced equation : 
Explanation:
A double displacement reaction is one in which exchange of ions take place. The salts which are soluble in water are designated by symbol (aq) and those which are insoluble in water and remain in solid form are represented by (s) after their chemical formulas.
The skeletal equation is:

The balanced chemical equation is:

HCN is a weak acid, with A Ka = 4.0 x 10-10.
Answer:
A series circuit is defined as the circuit in which a number of resistances are connected one after the other.. In a series circuit, the flow of current follows a single path.
A parallel circuit is defined as the circuit in which a number of resistances are linked across each other in such a way that one terminal of each resistance is connected to form a junction point while the remaining end is also connected to form another point.
You havent added the diagram so i cant tell you the answer, but i added the definition of each circuit, see if that helps!