How can I delete multiple lines in vi?

Question

I have tried to follow the following:

How to delete selected text in VI editor

but

5dd

gives

E492: Not a

Answer 1

I find this easier

1. Go VISUAL mode Shift+v
2. Select lines
3. d to delete

https://superuser.com/questions/170795/how-can-i-select-and-delete-lines-of-text-in-vi