How many businesses accept insurance?
business that accept insurance refers to attribute_name = 'Accepts Insurance' AND attribute_value = 'true'
SELECT COUNT(T1.business_id) FROM Business_Attributes AS T1 INNER JOIN Attributes AS T2 ON T1.attribute_id = T2.attribute_id WHERE T2.attribute_name = 'Accepts Insurance' AND T1.attribute_value = 'true'