CREATE TABLE table_204_975 (id NUMBER, "year" NUMBER, "competition" CLOB, "location" CLOB, "event" CLOB, "final-rank" CLOB, "final-score" NUMBER, "qualifying rank" NUMBER, "qualifying score" NUMBER)

what was the difference between her qualifying scores for balance beam between boston and philadelphia ?
SELECT ABS((SELECT "qualifying score" FROM table_204_975 WHERE "event" = 'balance beam' AND "location" = 'boston') - (SELECT "qualifying score" FROM table_204_975 WHERE "event" = 'balance beam' AND "location" = 'philadelphia'))
SELECT ABS((SELECT "qualifying score" FROM "table_204_975" WHERE "event" = 'balance beam' AND "location" = 'boston') - (SELECT "qualifying score" FROM "table_204_975" WHERE "event" = 'balance beam' AND "location" = 'philadelphia'))