where is the division symbol

Command-Shift-Space opens up a character chooser, and you can select most any Unicode character there.

That’s described here:

… Use emoji and symbols on Mac - Apple Support

For the ➗ symbol on macOS, use Option-/

if you want to see shortcuts (such as Option-/), use the Keyboard Viewer:

… Use the Keyboard Viewer on Mac - Apple Support

Here’s a third-party list of option key chords:

… https://www.webnots.com/option-or-alt-key-shortcuts-to-insert-symbols-in-mac-os-x/

If you are in Safari, go to Edit > Emoji & Symbols and it is listed under "Math Symbols. Just double click and it will show up like this: ÷. Other Apps may have it in a different location. You can also hold down the Option key and tap the "/" on the keyboard to display the same symbol.

You mean in the Character Viewer?