Firstly I wrote in my book the numbers 0-9 and then I wrote the numbers on the envelopes down and I put the numbers in a space each and wrote down all the outcomes that each sum could be. Then i saw witch numbers were being used in each sum and crossed out the numbers that could be used for each sum so there were know numbers that were in two sums. Then i realised that i had wrote the wrong envelope number so i had to start again. so i wrote all the sums down again and i worked it out and these are the possible outcome that the sum for eight could have been...
8
7+1
0+8
2+6
3+5
4+6
But with all of my other sums which were:
7 13 14 3
5+2 9+4 8+6 0+3
so the sum that i got for the number 8 on the envelope was:
8
7+1