Desafío libreta de calificaciones.

Mí problema es el siguiente, por más vcvuelta que le doy a este desafío, no logro conseguir que la segunda parte me salga correcta, he intentado durante horas y en realidad no he logrado avanzar; existe un post similar del 4 de marzo, pero no fué respondido, quisiera qué me dieran alguna pista del porque está dándome este problema, puede que sea una tontería, pero de verdad quiero comprender ese asunto.

PD. Gracias por la paciencia y la ayuda.

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CREATE TABLE student_grades (
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT,
number_grade INTEGER,
fraction_completed REAL);

INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winston", 90, 0.805);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winnefer", 95, 0.901);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winsteen", 85, 0.906);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Wincifer", 66, 0.7054);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winster", 76, 0.5013);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winstonia", 82, 0.9045);

Select * From student_grades;

Select count ("name, number_grade, ROUND (fraction_completed*100")) AS percent_completed FROM student_grades

SELECT "name",
CASE
WHEN number_grade > 90 THEN "A"
WHEN number_grade > 80 THEN "B"
WHEN number_grade > 70 THEN "C"
ELSE "F"
END as letter_grade

from student_grades
Select "name",
CASE

WHEN number_grade > 90 THEN "A"
WHEN number_grade > 80 THEN "B"
WHEN number_grade > 70 THEN "C"
ELSE "F"
END as letter_grade

Select "student_grade" CASE

WHEN number_grade > 90 THEN "A"
WHEN number_grade > 80 THEN "B"
WHEN number_grade > 70 THEN "C"
ELSE "F"",

Select "name" FROM "student_grades" WHERE "student_grades" IN ("A", "B", "C", "F")