Voltage output in ripple filter
Now this problem confuses me for instance i cannot figure out if they
  are parallel or series


Parallel connected circuit elements share the same voltage across, series connected circuit elements share the same current through.

In this case, and by KCL, it is clear that the capacitor current is identical to the resistor current so the resistor and capacitor are series connected.


  and therefore could not found impedance to find the output voltage


Well, you must proceed carefully here if you plan to use an impedance approach as your input voltage is the sum of a constant and a sinusoid

Since the impedance of the capacitor is "infinite" for a constant voltage, the constant term passes through to the output unchanged; only the sinusoid is affected.

For the sinusoidal component, there is attenuation by the factor:

\$\dfrac{1}{1 + j \omega RC} \$