SELECT count(*)
FROM  inspections, businesses, agencies
WHERE inspections.business_id = businesses.id
  AND businesses.agency_id = agencies.id
  AND agencies.slug = 'los_angeles'
  AND (CURRENT_DATE - inspections.date) <= 30



SELECT COUNT(*)
FROM  inspections
  INNER JOIN businesses ON inspections.business_id = businesses.id
  INNER JOIN agencies ON businesses.agency_id = agencies.id
WHERE agencies.slug = 'los_angeles'
  AND (CURRENT_DATE - inspections.date) <= 30