To create a linear equation that represents the total number of hair ties \( h \) based on the number of days \( d \) that have passed, we start with the initial number of hair ties Tommy already had (5) and then add the amount he steals each day (3).
The equation can be formulated as follows:
\[ h(d) = 5 + 3d \]
Here, \( h(d) \) represents the total number of hair ties, \( 5 \) is the starting number of hair ties, and \( 3d \) represents the total number of hair ties stolen after \( d \) days.