Suppose rendu resistor series irundha, rendu resistor laiyum same current thaan flow agum.so u can add the value of resistors and make it as single resistor....Now u can apply kcl
oru 'T' network eduthuko, idhula one node irukku reference node illama. so andha node ku KCL apply pannalaam...Idhuve Pi network la two nodes irukku, rendu nodes kum KCL apply pannalam....T and Pi network la resistors Parallel and Perpendicular ah connect irukkum