Complex sentence: Kleppin was the runner-up finisher at the 2014 USA Half-Marathon Championships, and third-place finisher at the 2014 Los Angeles Marathon, where she took 13 minutes off her previous marathon personal best.
Split into simpler sentences: Kleppin was the runner-up finisher at the 2014 USA Half-Marathon Championships. Lauren was the third-place finisher at the 2014 Los Angeles Marathon, where she took 13 minutes off her previous marathon personal best.