First find the number of cars not counting the engine and caboose: 71 cars - 2 cars = <<71-2=69>>69 cars
Let p be the number of passenger cars and c be the number of cargo cars. We know that p + c = 69 and c = p/2 + 3
Substituting the second equation into the first, we get p + p/2 + 3 = 69
Combining like terms, we get 1.5p + 3 = 69
Subtracting 3 from both sides, we get 1.5p = 66
Dividing both sides by 1.5, we get p = 44
#### 44