CREATE TABLE table_13306 ("Period" CLOB, "Internet Explorer" CLOB, "Firefox" CLOB, "Safari" CLOB, "Opera" CLOB, "Netscape" CLOB, "Other Mozilla" CLOB)

What percentage of users were using Opera during the period in which 63.67% were using Internet Explorer?
SELECT "Opera" FROM table_13306 WHERE "Internet Explorer" = '63.67%'
SELECT "Opera" FROM "table_13306" WHERE "Internet Explorer" = '63.67%'