CREATE TABLE table_7206 ("Objects" TEXT, "Date" TEXT, "SiO 2" FLOAT, "Al 2 O 3" FLOAT, "Fe 2 O 3" FLOAT, "K 2 O" FLOAT, "Na 2 O" FLOAT)

What is average SiO 2, when Na 2 O is 7.53, and when Al 2 O 3 is less than 2.13?
SELECT AVG("SiO 2") FROM table_7206 WHERE "Na 2 O" = '7.53' AND "Al 2 O 3" < '2.13'
SELECT AVG("SiO 2") FROM "table_7206" WHERE "Al 2 O 3" < '2.13' AND "Na 2 O" = '7.53'