Final answer:
The expression for the number of shirts Snard bought is 30 - x, where x represents the number of pants he bought.
Step-by-step explanation:
The expression for the number of shirts Snard bought can be written as 30 - x, where x represents the number of pants he bought.
This expression assumes that Snard bought either a shirt or a pair of pants for each of the 30 items. Therefore, the remaining items (30 - x) would represent the number of shirts he bought.