NUMBERS, PAGES and Keynote are office applications developed by Apple, which are corresponding with Excel, Word and PowerPoint, from Microsoft. If you have an older Mac model it is very possible that you can no longer install these applications. In this tutorial I show you step by step, how you install numbers, pages on the old maccos versions.
NUMBERS, PAGES and Keynote applications can only be installed from the App Store, being applications developed by Apple. The problem arises when you have an old poppy model, with Macos Catalina operating system (10.15) or older, and the new versions of the applications are no longer compatible. You must have a Macos 11 or newer version to be able to install NUMBERS, PAGES and Keynote from the App Store. Unfortunately, also because of Apple's limitations, this is impossible on older poppy models.
“We could not complete your purchase.
Numbers can’t be installed on “macOS” because macOS version 11 or later is required.”

How do you install Numbers, Pages on old macOS versions
In order to install NUMBERS, PAGES and Keynote on Macos Catalina (or older versions), you need the old versions of these applications. If you have had them in the past, the applications are kept in iCloud with the versions at that time, and can be downloaded from the App Store.
So, in order to install Numbers, Pages or Keynote on a Mac with Macos 10.15 or older operating system, the first condition is to have an Apple ID that you have in the past have installed these applications.
1. On the Mac or MacBook computer that you want to install NUMBERS, PAGES or Keynot, open the App Store, then go to your user, down.

2 (optional). In “Account” You have all the applications that have been installed through the App Store over time. Also from here, you can also access the list of applications of another family member, if he has Activated Family Sharing. You can install NUMBERS, PAGES or Keynote applications and from another family member, if he had installed them in the past.

3. Roll down (without using the search box), until you find the applications you want to install, then click on the download sign (download).

Related: How can you completely uninstall applications on macos
În acest fel, vei putea instala Numbers, Pages și Keynote pe vechile modele de Mac, care nu mai accepta noile versiuni macOS. Din App Store > Apple ID > Purchased, aplicațiile se vor instala cu vechile versiuni compatibile.