Show the sum of lesson prices per staff.
select t2.first_name, t2.last_name, sum(t1.price) from lessons as t1 join staff as t2 on t1.staff_id = t2.staff_id group by t2.staff_id
Give the average.
select t2.first_name, t2.last_name, avg(t1.price) from lessons as t1 join staff as t2 on t1.staff_id = t2.staff_id group by t2.staff_id
Just for first name as Janessa and last name as Sawayn?
select avg(price) 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";