Matt_Parker_2 | MPMSolution: David and Anton @mattparker2 | Uploaded 4 years ago | Updated 10 minutes ago
This is the solution to the David and Anton puzzle.
think-maths.co.uk/agepuzzle
youtu.be/4Gvku07K5NQ

Top mention for Gregor's page to generate and solve such puzzles!
mpmp-11.glitch.me

League table is here:
think-maths.co.uk/league-table

All details about Matt Parker's Maths Puzzles are on the Think Maths website:
think-maths.co.uk/maths-puzzles

David (37.5) and Anton's (27.5) ages combined are 65.
David (37.5) is currently thrice as old as Anton was (12.5)
when David (22.5) was half as old as Anton will be (45)
when Anton (45) is thrice as old as David was (15)
when David (15) was thrice as old as Anton (5).

All of the Alexander Shekhtman's working out:
drive.google.com/file/d/1tKeJQhBV_BTzJ64nZLgxjchiodKTzzYA/view?usp=sharing

Amy Strauss's spreadsheet:
docs.google.com/spreadsheets/d/1D2VEwRKyrocbAbob4oe-U-u4GYgNHUu801e2UcNtPCY/edit#gid=0

James Coutie's video:
youtu.be/UnW7Z07sxAU

I used pretty much this method when I first solved the puzzle.
http://primepuzzle.com/tunxis/mary's-age.html

Mees Broer's Desmos file:
desmos.com/calculator/elwbweekzl