Question

What are the input variable and the output variable? number of rowers in a rowboat and the speed of the rowboat?

Answer 1

You can establish a function that relates the speed of the boat to the number of rowers, i.e. spped of the boat, s = f (number of rowers)

I thing ther you can see that the input variable is the number of rowers and the output variable is the speed of the boat.

Answer 2

More rowers in a rowboat will increase the speed of a rowboat.
Answer:
The input variable: number of rowers.
The output variable: the speed of a rowboat.