Kirchhoffs Law

What is a junction? A junction is any place (in a circuit), where two o more wires come together/meet.
What is a branch? A branch is a anything that connects two junctions togheter.
How many junctions are  there in this circuit? 2
How many branch are  there in this circuit?3
 
Number of branches = Number of currents. This circuit has 3 branches, therefore, there are 3 separate currents.
Kirchhoffs law can be used for any circuit.
The current which enters the junction is positive, and the current which leaves the junction is negative.
Junction 1= -I1-I2+I3=0
Junction 2= I1+I2-I3=0
 There are 3 posibles loop rule equiations in this circuit:
-Top loop.
-Bottom loop.
-Complete loop.
If a current passes through a battery, negative to positive, then the voltageis positive. If a current passes through a battery, positive to negative, then the voltage is negative.
Step 1= 24V-2I1-4I1-3I1+3I2= 0
              24V-9I1+3I2=0
Step 2= 12V-3I2+3I2-1I2-5I2=0
              12V+3I1-9I2=0