Final answer:
To represent Simon's past jumps, which are less than his longest jump of 38 units, the correct inequality symbol is '<' (less than), demonstrated by the inequality x < 38.
Step-by-step explanation:
The question asks about selecting the appropriate inequality symbol to represent the jumping distances less than Simon's longest jump of 38 units. We can use an inequality symbol to show that Simon's past jumps were shorter than 38. Therefore, the symbol that should be used to complete the inequality for Simon's past jumps is '<' (less than), which indicates that Simon's past jumping distances are less than 38 units. An example of such an inequality would be x < 38, where x represents Simon's past jumping distances.