7. (10 points) A convoy passes through a 298-meter-long bridge at a speed of 4 meters/second, taking a total of 115 seconds. It is known that each vehicle is 6 meters long, and the interval between adjacent vehicles is 20 meters. Then, this convoy has $\qquad$ vehicles.

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【Analysis】The distance the convoy travels over the bridge is the length of the convoy plus the length of the bridge. The length of the convoy: $115 \times 4 - 298 = 162$ (meters), the number of gaps between the cars is: $(162 - 6) \div (20 + 6) = 6$, so the total number of cars in the convoy is: $6 + 1 = 7$; according to this, solve the problem.

【Solution】Solution: According to the analysis,
The length of the convoy: $115 \times 4 - 298 = 162$ (meters),
The number of gaps between the cars is: $(162 - 6) \div (20 + 6) = 6$ (gaps),
The total number of cars is: $6 + 1 = 7$ (cars);
Answer: The convoy has a total of 7 cars.
Therefore, the answer is: 7.