Count the lesson time grouped by staff id.
select t2.staff_id, sum(lesson_time) from lessons as t1 join staff as t2 on t1.staff_id = t2.staff_id group by t2.staff_id
Join that sum on the staff with first name Janess and last name Sawayn.
select sum(lesson_time) from lessons as t1 join staff as t2 on t1.staff_id = t2.staff_id where t2.first_name = "Janessa" and t2.last_name = "Sawayn";