On how many projects where the teacher has ordered between 5 to 10 items are from are from Quill.com?
ordered between 5 to 10 items refers to item_quantity between 5 and 10; are from Quill.com refers to vendor_name = 'Quill.com'
SELECT COUNT(projectid) FROM resources WHERE vendor_name = 'Quill.com' AND item_quantity BETWEEN 5 AND 10