Find I_1 in the network.
Image from: Irwin, J. David., and R. M. Nelms. Basic Engineering Circuit Analysis, Tenth Edition. N.p.: John Wiley & Sons, 2010.
We will write Kirchhoff’s current law for nodes A and B (which were arbitrarily chosen). (Forgot Kirchhoff’s current law?)
(here, we assigned I_2 as the current coming into the node)
This question can be found in Basic Engineering Circuit Analysis, 10th edition, chapter 2, question 2.10.