The formula to calculate the L Plate Hours (L) is:
\[ L = T - (S + P) \]
Where:
Let's say the total driving hours (T) is 120, the supervised driving hours (S) is 80, and the professional driving hours (P) is 20. Using the formula:
\[ L = 120 - (80 + 20) \]
We get:
\[ L = 20 \]
So, the L plate hours is 20.