Question

If it takes 726 W of power to move a mass 36 m and 14 seconds what is the mass

Answer 1

power = work / time
work = force * displacement
force = mass * gravity

so:

power = (mass * gravity * displacement) / time
726 = (mass * 9.81 * 36 ) / 14
726 * 14 = mass * 9.81 * 36
10164 = mass * 353.16
mass = 10164 / 353.16

mass = 28.78 kg

Answer 2

From that information, I can tell that the force pushing on the mass
averaged (282 and 1/3) newtons during those 24 seconds.

But the information doesn't nail down what the mass must be.
I think it would if we only knew something about the friction.
Either tell us how much friction there is, or tell us that there's
none, and I think I could find the mass.