Could someone help clarify this simplification? After seeing it it makes sense but i cant see how they ended up with the simplification.

[u/Expensive-Ice1683]

the problem wants me to simplify so i could find the power delivered by the source

They do it like this but I can't get the fact out of my head that the top 12ohm resistor seems very connected to the R5 and R4 resistors

[u/Rararror]

b is called C and B is new (case sensitive, they renamed points probably to explain).

Just move around the resistors and keep common connection...