Calculating voltage drop across capacitor
Here is one approach:  Temporarily remove the capacitor from the circuit.  Consider where the capacitor went the "output", and reduce the circuit to a Thevenin source.  Now you have a single voltage source with a single resistor in series with it driving a capacitance.  You should be able to calculate the voltage across the capacitor from there.

Remember that Ohm's law also works with capacitors, but that then the resistance is a complex impedance instead.  Note that when the resistance is actually just a resistor, it has no imaginary component and you get the traditional Ohm's law for resistors.  One way to think of that is that the "real" Ohm's law is for complex impedances, but the common version for resistance is just a special case where all the values are real.