CREATE TABLE table_52648 ("Driver" TEXT, "Constructor" TEXT, "Laps" FLOAT, "Time/Retired" TEXT, "Grid" FLOAT)

What was Jack Brabham's highest grid when his laps were more than 90?
SELECT MAX("Grid") FROM table_52648 WHERE "Driver" = 'jack brabham' AND "Laps" > '90'
SELECT MAX("Grid") FROM "table_52648" WHERE "Driver" = 'jack brabham' AND "Laps" > '90'