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(i) In order to get a resistance of 9 from three resistors of 6 each, we connect two 6 resistors in parallel and then this parallel combination is connected in series with the third 6 resistor .

For parallel connection:

Or R= 3

And for series connection: R= 3 + 6= 9

(ii) In order to get a resistance of 4 , their are multiple cases
(a) 1st Case
From three resistors of 6 each, we connect all the three 6 resistors in parallel:

Or R= 2

Then, Net Resistance R= 2+ 2= 4.
(b)2nd Case
We connect two resistors of 6 Ω in series and another resistor of 6 Ω in parallel to them
R= 6 Ω + 6Ω= 12Ω
Then Net Resistance 
Then R= 4 Ω