Calculate the average age of the male patients that have hypertension.
average age = AVG(DIVIDE(SUBTRACT(deathdate is null WHERE (julianday(substr(datetime('now'), 1, 10)))), julianday(patients.birthdate)), 365); male refers to gender = 'M'; hypertension refers to conditions.DESCRIPTION = 'Hypertension'
SELECT SUM(CASE WHEN T2.deathdate IS NULL THEN ROUND((strftime('%J', date('now')) - strftime('%J', T2.birthdate)) / 365) ELSE ROUND((strftime('%J', T2.deathdate) - strftime('%J', T2.birthdate)) / 365) END) / COUNT(T2.patient) FROM conditions AS T1 INNER JOIN patients AS T2 ON T1.PATIENT = T2.patient WHERE T1.DESCRIPTION = 'Hypertension' AND T2.gender = 'M'