Help a girl out please

1. I forgot how you write it but it adds 1/3 of the number, so for example 9/3 is 3, so you add 3 to 9 = 12 and then 21/3 is 7 and so you add 7 to 21 = 28. I forgot how you would write this but I know the answer is not 1/3 though because then that would be dilating. (srry this one isn't clear)

Also sorry I couldn't really help more I'm not very good at this stuff.

if x = 1, then the answer is 3.5