Answer:
b) Â Â V_CD = - V_AB , Â c) Â Â Â V_AD = -2 V_AB
Explanation:
b) In this exercise of potential differences they indicate that the diagonal potential is the negative of the leg potential
   V_AC = - V_AB
   V_BD = - V_CD
Thus
     V_CD = V_AC
Finally
      V_CD = - V_AB
c) The potential is a scalar quantity so it can be added algebraically, they give us the condition
     V_AC = -V_AB
     V_AB + V_BC = - V_AB
     V_BC = - 2 V_AB
For the other triangle
     V_BD = V_AC
     V_AB + V_AD =  V_AC
We replace
     V_AB + V_AD =  - V_AB
     V_AD = -2 V_AB