To find the monthly decrease in the car's value, you need to divide the total decrease in value by the number of months.
The car's value decreases by $2,500 over 6 months.
To calculate the monthly decrease:
\[ \text{Monthly decrease} = \frac{-2500}{6} \]
Now, let's divide:
\[ \frac{-2500}{6} \approx -416.67 \]
Therefore, the value decreases by approximately -$416.67 per month when rounded to the nearest hundredth.
So the answer is:
-$416.67