Can anyone can tell what is wrong with my code given below?

Question

The university gives students discounts on tuition fees depending on their performance:
90-100 => 50%
80-89 => 30%
70-79 => 10%
0-69 => 0%
Write a program that will take the scores from the first and second semesters, then calculate the average score, and output the result, depending on the score.

And my code is down below but it didn't showing anything can anyone can tell what is wrong in this code?

sem1_score = int(input())
sem2_score = int(input())
grade = sem1_score + sem2_score / 2
if grade >= 90 and grade <= 100:
print("50")
elif grade >= 80 and grade <= 89:
print("30")
elif grade >= 70 and grade <= 79:
print("10")
elif grade >= 0 and grade <= 69:
print("0")

Answer 1

grade = (sem1_score + sem2_score)/2