Table schema:
CREATE TABLE ENROLLED_IN (Grade VARCHAR, StuID VARCHAR); CREATE TABLE STUDENT (LName VARCHAR, StuID VARCHAR); CREATE TABLE GRADECONVERSION (gradepoint INTEGER, lettergrade VARCHAR)

Question: Find the average grade point of student whose last name is Smith.
SQL: SELECT AVG(T2.gradepoint) FROM ENROLLED_IN AS T1 JOIN GRADECONVERSION AS T2 JOIN STUDENT AS T3 ON T1.Grade = T2.lettergrade AND T1.StuID = T3.StuID WHERE T3.LName = "Smith"