Final answer:
The number of additional cars that can be stored in the lay-up yard is 34.
Step-by-step explanation:
The lay-up yard can hold a total of 5 ten-car trains. Currently, there are already 3 cars stored on each of the first 4 tracks, and 4 cars stored on the fifth track. To find the number of additional cars that can be stored in the yard, we need to find the total number of cars already stored and subtract it from the maximum capacity of the yard. So, the additional cars that can be stored in the yard is:
Total capacity - Total cars stored = 5 * 10 - (3 * 4 + 4) = 50 - 16 = 34 cars