Fix Linux install instructions

Author: Bisaloo

learners/setup.md

@@ -54,14 +54,12 @@ You have to install R before you install RStudio.
 
 ::::::: spoiler
 
-## For Linux 
+## For Linux
 
-* Download R from the [CRAN website](https://cran.r-project.org/bin/macosx/).
-* Select the `.pkg` file for the latest R version
-* Double click on the downloaded file to install R
-* It is also a good idea to install [XQuartz](https://www.xquartz.org/) (needed by some packages)
+* Click on your distribution in the [Linux folder of the CRAN website](https://cran.r-project.org/bin/linux/).
+* Go through the instructions for your distribution to install R.
 * Go to the [RStudio download page](https://www.rstudio.com/products/rstudio/download/#download)
-* Under *Installers* select **Your Version of Linux - RSTUDIO-xxxx.yy.z-zzz.dmg** (where x = year, y = month, and z represent version numbers)
+* Select the relevant installer for your Linux system (Ubuntu/Debian or Fedora)
 * Double click the file to install RStudio
 * Once it's installed, open RStudio to make sure it works and you don't get any error messages.