SELECT SUM("enrollment") FROM table_203_518 WHERE "type" = 'private/catholic'
how many are enrolled in private/catholic ?
CREATE TABLE table_203_518 (
    id number,
    "institution" text,
    "location" text,
    "nickname" text,
    "founded" number,
    "type" text,
    "enrollment" number,
    "joined\nmac" number
)