This is another Pythagorean min.

We use d=rt to minimize the time. t=d/r.

The distance through the snow is:

The distance along the roa is

You are given the rates, so the time is:

That is what must be minimized. Set to 0 and solve for x.

That will be the distance from the point directly across from where the snowmobile ran out of gas to where you must walk to in oreder to minimize the time.