The resistances are added in series. The effective resistance offered by a combination of two resistors in series with a 4 ohms resistor is 10 ohms which means that the equivalent resistance of two resistances in parallel connection must be 6 ohms. Suppose one resistor is "a" ohms and the other resistor is "b" resistors then the equivalent resistance will be . Therefore, 8 ohms and 24 ohms resistors will be the correct answer.