Forces and collision problem ? which equation to use?

Question

A box rests on a frozen pond, which serves as a frictionless horizontal surface.

If a fisherman applies a horizontal force with magnitude 54.0 N to the box and produces an acceleration of magnitude 3.40 m/s^2, what is the mass of the box?

Answer 1

F = m*a

m = F/a

m = 54/3.4 kg

This assumes the fisherman is not also on the ice and doesn't move.