We have equation of motion v = u + at
Where v = final velocity, u = initial velocity, a = acceleration, and t = time
In this case car is travelling in -x direction
Velocity of car = displacement / time
Since displacement value is increasing in negative x axis it's initial velocity is negative
And it's final velocity is zero since it comes to rest, and time is also positive
So, v= u+ at => 0 = -u + at
So, a = u/t
Which is positive and along positive X - direction
