i just bought a macbook Air how do I know what system is on it

Hi,

To see your the operating system of your MacBook, follow these instructions.

If it's new and bought from Apple then you have macOS Big Sur.

If it's second hand then click the menu > About > here

On the Desktop Apple Icon >> About this Mac >> next windows opens and will tell what version of macOS is installed. ( ie: Big Sur, Catalina, Mojave ec. )

Hi,

This article will help you.