In a parallel connection, the voltage is same in every branch.
Now, three 
three resistors connected in parallel. 
R1 = 2k ohm
R2 = 6k ohm
R3 = 10k ohm
in parallel, net resisitance = 

Now, putting the values, we get, R net = 1.30 k ohm.
Ans, voltage = 100 VDC
Thus, power = 
 
 
 = 7.69 Watt