Error on this line: pragma solidity ^0.4.21 ;

I followed the video ‘Intro to Cryptoeconomics’ and wrote the code into the Remix from Etheruem, but the version in the video for pragma solidity seems to be outdated. I’ve tried replacing it with the newest version but it does no good. I can not run the program.

Full disclosure, this is my first coding or rather copy of the syllabus.

Can anybody help?