Because resistors A, B and C are connected together in parallel, the directions of the currents through the three resistors are the same. Since the current through resistor A is directed to the left, the currents through resistors B and C are also directed to the left.
The three-resistor network containing resistors A, B and C is equivalent to the resistor on the left labeled ‘ABC’. The word ‘equivalent’ means that the voltage, current and resistance of resistor ABC are equal to the voltage, current and resistance of the three-resistor parallel network. In particular, the current which is directed to the left in the three resistor network must also be directed to the left through resistor ABC.
Resistors A and B are connected together in parallel. Together, they are equivalent to the single resistor on the left labeled ‘AB’. The word ‘equivalent’ means that the voltage, current and resistance of resistor AB are equal to the voltage, current and resistance of the two-resistor parallel network. In particular, the current that is directed to the left through resistor AB must also be directed to the left through both resistors A and B. Thus the currents through resistors A and B are both directed to the left.