(2) When a=320:
Residual oil in the oil tank = 20-0.06x320 = 0.8 > 0.
∴ There is enough oil in the fuel tank;
(3) According to the meaning of the question:
20-0.06a≥0
∴0.06a≤20
∴a≤ 1000/3
A is an integer.
The maximum integer value of ∴a is 333.
Then, the maximum integer value that can guarantee the driving distance of the car is 333 kilometers.
I am glad to solve the above problems for you, and I hope it will help your study! ≤、≥ ∠