3 = 2.999999999999…

I remembered this today and don’t want to forget it.

x = 3 and y = 2.9
10x – x = 9x and 10y – y = 9y
30 – 3 = 27 and 29.9 – 2.9 = 27
9x = 27 = 9y
9x = 9y
x = y
therefore 3 = 2.9 (?)