CREATE TABLE table_67527 ("Institution" TEXT, "Team" TEXT, "City" TEXT, "Province" TEXT, "First season" FLOAT, "Head coach" TEXT, "Enrollment" FLOAT, "Football stadium" TEXT, "Capacity" FLOAT)

What is the average capacity of stadiums in the City of London that belong to schools with an enrollment less than 30,000?
SELECT AVG("Capacity") FROM table_67527 WHERE "City" = 'london' AND "Enrollment" < '30,000'
SELECT AVG("Capacity") FROM "table_67527" WHERE "City" = 'london' AND "Enrollment" < '30,000'