How do you arrange six 6-ohm resistors to have a total resistance of 6-ohm?
simulate this circuit &ndash; Schematic created using CircuitLab

here R5//R1 series to R3 => 3 + 6 = 9 in one branch

R4 + R6 + R2 => 6 + 6 + 6 = 18 in 2nd branch 

18 // 9 gives 6