Explanation:

Introduction:
The given relation V = A - av - bt - c represents the volume (V) of a liquid crossing through a tube in terms of the area of cross-section (A), velocity (v), and time (t). We need to determine if a is equal to b + c or not.

Analysis:
To analyze the correctness of the given statement, let's break down the equation and compare the coefficients of the variables.

1. Coefficient of A:
- The coefficient of A is 1.
- This indicates that the volume of the liquid is directly proportional to the area of the cross-section.

2. Coefficient of v:
- The coefficient of v is -a.
- This implies that the velocity of the liquid has a negative influence on the volume.
- A higher velocity will result in a decrease in the volume of liquid crossing through the tube.

3. Coefficient of t:
- The coefficient of t is -b.
- This suggests that the time taken for the liquid to cross through the tube has a negative impact on the volume.
- As the time increases, the volume of liquid crossing through the tube decreases.

4. Constant term:
- The constant term is -c.
- This represents any other factors that may affect the volume but are not dependent on the cross-sectional area, velocity, or time.

Conclusion:
Based on the analysis, we can conclude that a is not equal to b + c. The coefficients of v and t have different values (-a and -b) in the equation, indicating that the velocity and time have distinct impacts on the volume of the liquid crossing through the tube. The constant term (-c) represents any additional factors affecting the volume.