I DONT know FiGURE it out YOURSELF
<span>Assuming the car is travelling in the same direction for the entire hour, the acceleration is zero.</span>
I can't answer this question without a figure. I've found a similar problem as shown in the first picture attached. When adding vectors, you don't have to add the magnitudes only, because vectors also have to factor in the directions. To find the resultant vector C, connect the end tails of the individual vectors.
<em>The red line (second picture) represents the vector C.</em>
When the car comes to a stop, the final velocity must be 0 m/s.
Since the car js decelerating in a forward direction, acceleration must be negative.
final v = initial v + a•t
0 = 20 + (-6)t
t = 3.33s