Question

Two resistence when connected in parallel give a resultant the value of 2 ohm when connected in series the value becomes=9 ohm

Answer 1

One will be 6 ohm and the other will be 3 ohm.
When connected in parallel:-
Rp = 2 ohm (by calculation)
When connected in series:-
Rs = (6+3)ohm= 9 ohm.

Answer 2

let the two resistance R1 and R2 

Now R1 + R2 = 9 
R1= 9- R2 

according to parallel combination 

(1/ 9-R2) + (1 /  R2)  = 2 

R2 +9 -R2 = 2 ( 9 R2 - R2 ² )

9 = 18R2 - 2 R2 ²

-2R2 ² + 18 R2 -9 = 0 

2R2² - 18R2 + 9   = 0 

a = 2 
b = -18 
c = 9 
D = b² - 4ac 
   = 324 - 4 . 2. 9 
   = 324 - 72
   = 252 
two values are 

R2 = 18 + √252 / 4 and 18 - √252/4
     =  18 + 15.87 / 4 and 18 - 15 .87 / 4 
     =  8.46 and 0.53