The maximum value of d is such that the bear gets to the car at the same time the tourist does.

So set up a coordinate system such that the bear is at the origin and positive x is in the direction from the bear to the tourist.

Both are moving at a constant speed. The bear has to cover 27 + d meters in the same time the tourist covers d meters.

So for the tourist:

[tex]d = v_t t = 3.5t[tex]

Thus

For the bear:

Now solve for d.

-Dan