Four resistors of 12, 3.0, 5.0, and 4.0 W are connected in series. A 12-V battery is connected to the combination. What is the current through the battery?

Kirchhoff's junction rule: At any junction point, the sum of all the currents entering the junction must equal the sum of all the currents leaving the junction.
Kirchhoff's loop rule: The sum of the changes in potential around any closed path of a circuit must be zero.