một xe lửa cần vận chuyển một lượng hàng , người lái xe tính rằng nếu xếp mỗi toa 15 tấn hàng thì còn thừa lại 5 tấn ,còn nếu xếp mỗi toa 16 tấn thì có thể chở thêm 3 tấn nữa .hỏi xe lửa có mấy toa va...

To solve this problem, we can use a system of equations. Let's denote the number of cars as $$ and the amount of cargo in tons as $$. From the given information, we can set up the following system of equations: $$ We can solve this system by first solving for $$ in both equations: From the first equation: $$ From the second equation: $$ Since both expressions are equal to $$, we can set them equal to each other: $$ Solving for $$, we get: $$ Now that we have found the value of $$, we can substitute it back into one of the original equations to find the value of $y. Let's use the first equation: $$ So, the train has -8 cars and carries -125 tons of cargo.