Step 1: Identify common codes.
'123' = 'I am going'.
'345' = 'I was eating'.
'146' = 'She was going'.
Step 2: Matching words.
'going' is common between '123' and '146'.
Numbers common between 123 and 146 are 1 (and maybe others).
Thus, 1 likely represents 'going'.
Now focus on '345' ('I was eating'). Since '1' is 'going', and '3' and '5' remain, and 'eating' is not mentioned anywhere else.
Thus, '5' stands for 'eating'.