Find V_{ad} in the circuit.
Image from: Irwin, J. David., and R. M. Nelms. Basic Engineering Circuit Analysis, Tenth Edition. N.p.: John Wiley & Sons, 2010.
Solution:
Between the nodes “a” and “d” the total voltage should be 0 in accordance with Kirchhoff’s voltage law. (Forgot Kirchhoff’s voltage law?) We can write the following equation to find V_{ad}.
V_{ad}+3V+2V=12V
V_{ad}=7V
This question can be found in Basic Engineering Circuit Analysis, 10th edition, chapter 2, question 2.24.