In short, the current through the resistor is never anything but real, so you'll never see a 3+5i current through a resistor.
The current through the resistor is always in phase with the voltage so you'll never see anything but 3 or 7 or 0.234 or whatever.
That's the ideal resistor.
Please have a look on the attachment. I first found the current through the capacitor, Ic. Then, I found the voltage across the capacitor, which is same as across the 4 ohm resistor, hence V_4Ω. Then, I used the formula: (1/2)Vm*Im*cos(θv-θi), Vm and Im are magnitudes of voltage and current. Please help me. Thanks.