Complex sentence: The exhibition was opened by Princess Alexandra, wife of Edward, the Prince of Wales on 3 May 1887, and remained open for 166 days, during which time there were 4.5 million paying visitors, 74,600 in one day alone.
Split into simpler sentences: The exhibition was opened by Princess Alexandra, wife of Edward, the Prince of Wales on 3 May 1887. It remained open for 166 days, during which time there were 4.5 million paying visitors, 74,600 in one day alone.