Let \( s \) represent the number of shirts that Demetrius wants to buy. The cost of each shirt is $16. If he can spend a maximum of $50 on shirts, the total cost of the shirts can be expressed as \( 16s \).
To represent the situation as an inequality, we express that the total cost of the shirts should be less than or equal to $50:
\[ 16s \leq 50 \]
This inequality indicates that the total cost of the shirts Demetrius buys cannot exceed $50.