Help pls quick! And ty

X+ y = 5 ; x - y =3 solve using linear combination

The american academy of pediatrics wants to conduct a survey of recently graduated family practitioners to assess why they did not choose pediatrics for their specialization. provide a definition of the population, suggest a sampling frame, and indicate the appropriate sampling unit.

Anyone? 15m is what percent of 60m; 3m; 30m; 1.5 km?