Question

Find R equivalent for A to C.

Answer 1

R1 = 2 ohm
R2  =3 ohm
R3 = 4 ohm
R4 = 6 ohm

This is a Wheatstone Bridge coz 
R1/R2 = R3/R4

So, The diagonally connected wire can be neglected

Hence R1 and R2 are in series 
Req = 2 + 3 = 5 ohm

Similarily, R3 and R4 are in series 
Req = 4 + 6 = 10 ohm

PARALLEL COMBINATION

1/Req = 1/10 + 1/5
1/Req = 3/10

Req = 10/3

Req = 3.33 ohm

Answer 2

total resistance=1/5+1/5+1=7/5

resistance=5/7 ohm