Solve the system of equations ∣a1−a2∣x2+∣a1−a3∣x3+∣a1−a4∣x4=1∣a2−a1∣x1+∣a2−a3∣x3+∣a2−a4∣x4=1∣a3−a1∣x1+∣a3−a2∣x2+∣a3−a4∣x4=1∣a4−a1∣x1+∣a4−a2∣x2+∣a4−a3∣x3=1 where a1,a2,a3,a4 are four different real numbers.
Official text Transcription from AI-MO AoPS, checked word for word against the official paper. Quoted with source.