Balanced three phase circuit Y-Y with neutral
You need:


an equation for the current through your line, in terms of VAN. (Hint: the voltage across the line is 240 - VAN. Use Ohm's law.)
an equation for the current through the combined load of L1 and L2, in terms of VAN. (Hint: Consider L1 and L2 as a single load absorbing 630W and 840var. Use S=V*I)


These two currents are equal so you should be able to solve for VAN.