Warning! It seems that you are using Dodona within another webpage, so not everything may work properly. Let your teacher know so that he can solve the problem by adjusting a setting in the learning environment. In the meantime, you can click this link to open Dodona in a new window.
import math
# Invoer
n = int(input("Geef het aantal bomen in: "))
percentage = int(input("Geef het percentage in: "))
bijplanten = int(input("Geef het aantal nieuwe bomen in: "))
# Berekening
print("Er zijn eerst", n, "bomen in het bos.")
You can submit as many times as you like. Only your latest submission will be taken into account.