Step 1: Sort the three thermal joining processes by filler melting point.
Soldering, brazing and welding are generally told apart by how hot the filler metal (and in welding's case, the base metal too) needs to get, with soldering being the coolest of the three by definition.
Step 2: Pin down the defining temperature line for soldering.
By convention, soldering uses filler alloys, called solders, that melt below 450 degrees Celsius, this is what separates it from brazing, which uses filler metals melting above that mark even though the joining mechanism looks similar.
Step 3: Narrow down to the actual working range.
Common solder alloys, such as traditional tin lead solder or modern lead free tin silver copper solder, melt at temperatures roughly between 150 and 230 degrees Celsius, so the practical working temperature for soldering typically falls in the 150 to 300 degrees Celsius band, comfortably below both brazing and welding temperature ranges.
\[ \boxed{150 \text{ to } 300^\circ C} \]