HEAT

Let 'r' be the resistance of the electric kettle,  v₁= 22o v , t₁ = 6.5 min , v₂= 200 v , t_{2 =} ?

 As the heat produced in both the cases will be same ,

Use the relation, 

heat produced =   v₁² t₁ / r =  v₂² t₂ / r     

and plug in the values , to get the time t₂, required if the supply had been 200V  .