@Dave7 @twentysix by twentyfive @Rasmus @jefmcg @Supersuperleeds @Tim Hall @vernon
@classic33 @PhilDawson8270 @ClichéGuevara
Thank you everyone for your ideas. My dad had a lovely birthday.
I wrote various ways of expressing 80 around the envelope; 80 and the date in binary, roman numerals, the equations from jef made into a subtraction, four score and AT.
I made a quiz of 12 questions about 80 based on Vernon's idea, which included everyone else's ideas too plus a couple I made up ( @ anyone get this?) plus some ideas I got by googling.
I also made a simple code to put inside the card because he used to make them for me when I was young.
My dad absolutely loved all of it and they've been showing all their friends.
I'll save the homophones idea for my mum's 80th in a few years as she likes words. I'll try and make her a cryptic cross word as she's good at them.
PS there's a mistake on the envelope, that my dad spotted! I finished it late on Sunday night ready to post in the morning.