How long does student Linda Smith spend on the restaurant in total?
SELECT sum(Spent) FROM Student JOIN Visits_Restaurant ON Student.StuID = Visits_Restaurant.StuID WHERE Student.Fname = "Linda" AND Student.Lname = "Smith";
total time spent by Linda Smith in the restaurant refers to SUM(Spent); joining tables to relate Student and their visits to restaurant; first name and last name filtering refers to WHERE Student.Fname = 'Linda' AND Student.Lname = 'Smith';