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

1. Esc to exit insert mode
2. :1enter go to line 1 (replace '1' with the line you are interested in)
3. 5dd delete 5 lines (from the current line)

Type :set number (for numbered lines).