We don't know if the road is perfectly straight between the intersections, or if the road bends, curves, or turns between them. So we don't have enough information to calculate the displacement between them.
But we <em>can</em> calculate the <u>distance</u> the car traveled between them.
Distance = (speed) (time)
Distance = (20 m/s) (120 s)
<em>Distance = 2,400 meters</em>