Find the p.d across each capacitor is10 micro farads is charged by an 80v supply and then connected across an uncharged 20micro farads capacitors

so, you have an 10 and 20 microfrad inparallel.

Initial charge was q=CV=10*80 microcoulombs=800e-6 coulombs
Now, after the charge the total capacitance is 30 microfarad, so the parallel voltage is V=q/C=800/30=23.3 volts