Take the Riverside Line to Union Station LA, than take the Subway until you reach the Blue Line, Take the Blue Line to Willowbrook, than take the Green Line to LAX, after that to get into the airport, take a bus, ride share, or walk.
The train (Metrolink) will go to LA Union station. From there there is a Flyover Bus to LAX or maybe use Lyft or Uber. I don't think the subway goes there.
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