Complex sentence: Dunn showed the horse to the three-year-old World Championship at the 1997 Tennessee Walking Horse National Celebration and the four-year-old World Championship in 1998 RPM was entered in the open World Grand Championship and won reserve.
Split into simpler sentences: Dunn showed the horse to the three-year-old World Championship at the 1997 Tennessee Walking Horse National Celebration and the four-year-old World Championship in 1998. The same year, RPM was entered in the open World Grand Championship and won reserve.