Many circuits have resistors in both series and parallel. To find the total current through the circuit you generally want to replace the set of resistors with its equivalent resistor. This can be done by identifying a pair of resistors that is either in series or in parallel, replacing that pair by a single equivalent resistor, and iterating until you're left with one resistor in the circuit.

This allows the total current in the circuit to be determined. The current flowing through each resistor can then be found by undoing the reduction process.