Let the combined parallel resistance of 3 Ω and x = Q Ω ∴ Total resistance in the circuit = 2 + Q + 1.5 = 3.5 + Q Ω Total current in the circuit = 2A P.D a cross the circuit 12 volts ∴ From Ohm’s law, V = IR 12 = 2(3.5 + Q) = 7.0 + 2Q ∴ 2Q = 12 – 7 = 5 ∴ Q = 5/2 = 2.5 Ω Thus from parallel formula: I/Q = 1/3 + 1/x 1/2.5 = 1/3 + 1/x ∴ 1/x = 1/2.5 - 1/3 = 3-2.5/7.5 = 0.5/7.5 X = 7.5/0.5 = 75/5 = 15 Ω ∴ X = 15 Ω