What makes this word problem rational, and what would be the rational equation equivalent of it?

The problem is:
Two mules can finish carrying their loads from the start point, to the finish point, in 4 hours. A
very strong, very durable horse joins their team, and they finish in half the time (2 hours). If the
horse were to deliver the loads on his own, how long would it take the horse to carry the loads
from the start point to the finish point?

Question

What makes this word problem rational, and what would be the rational equation equivalent of it?

The problem is:
Two mules can finish carrying their loads from the start point, to the finish point, in 4 hours. A
very strong, very durable horse joins their team, and they finish in half the time (2 hours). If the
horse were to deliver the loads on his own, how long would it take the horse to carry the loads
from the start point to the finish point?

anonymous · Answer

I believe the answer would be *4 hours* for the horse to finish delivering the load by himself, but I can't think of what the rational equation equivalent of the word problem.

anonymous · Answer

If someone could help I'd be v thankful!