If Jared counted 300 cars, and Ann counted 15% more, then Ann counted 1.15 * 300 = 345 cars.
If Ann counted 7 cars more than their friend Alfred, then Alfred counted 345 - 7 = 338 cars.
The total number of cars counted by all of them will be 338 + 345 + 300 = <<338+345+300=983>>983 cars
#### 983