There are several possible problems here. One is that you did not set the default parameter correctly. Another, more likely problem, is that you didn't set it to change to the default parameter when necessary.
First, be sure that you've set your default parameter and made that equal to 10 and that is the last parameter set in the function.Â
Second, be sure that you call the function the way you need to. Do that as follows:
Ask for user input.
Set an if-else statement outside of your function. This needs to call the function with or without arguments, depending on the user input. It should look something like this:
if user_input > 0:
calculate_area(user_input)
else:
calculate area()
Note that the second option relies on the default value.