Since \( JL \) is the perpendicular bisector of \( KM \), it means that \( KH = HM \). We can set up the equation based on the information provided about the lengths \( KH \) and \( HM \):
\[ KH = HM \]
We know:
\[ KH = 6y + 3 \] \[ HM = 2y + 7 \]
Setting them equal to each other gives us the equation:
\[ 6y + 3 = 2y + 7 \]
Now, we can solve for \( y \):
- Subtract \( 2y \) from both sides:
\[ 6y - 2y + 3 = 7 \ 4y + 3 = 7 \]
- Subtract 3 from both sides:
\[ 4y = 4 \]
- Divide both sides by 4:
\[ y = 1 \]
Now we can find the length of segment \( HM \):
\[ HM = 2y + 7 = 2(1) + 7 = 2 + 7 = 9 \]
Thus, the length of segment \( HM \) is \( \boxed{9} \) units.