Question

how will you connect three resistors of each 9ohm to get equivalent as 6ohm

Answer 1

Take two resistor in series and then one in parallel.
In series
R=R1+R2
R=9+9
R=18ohm
Now in parallel
1/R=1/R1+1/R2
1/R=1/18+1/9
1/R=1+2/18
1/R=3/18
1/R=1/6
R=6Ohm
Hope it hlps u.

Answer 2

Connect two resistors in series and the other one parallel to them
So... Rs = 18
Rp = 1/18 + 1/9
    = 1/18 + 2/18
    = 3/18
       = 1/6
thus, total eq. R = 6 ohm