Find Vad in the circuit

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.