Problem
First name
Connor
Country
Age
10
File
First, I figured out which cards couldn't add up to 8 (4 & 9).
Next, figured out which cards could add up to each number on the envelopes.
Finally, I used to trial and error to see which combinations could work, starting with 1 & 2 in the 3 envelope. It worked!
My solution is that 0 & 8 are in the 8 envelope.