Acar accelerates from 30 km/hr to 65 km/hr in 30 seconds. what is it's acceleration?

Acceleration = (change in speed) / (time for the change).

                   =  (35 km/hr) / (30 sec)

                   =    7/6  km/hr-sec   .

To get rid of that ugly unit, and change the solution to a
more familiar unit of acceleration, we need to convert it
to the usual  ' m/s² '.  This is not a major operation.

                   (7/6  km/hr-sec) x (1000 m/km) x (1 hr/3600 sec)

             =    (7/6 x 1,000 ÷ 3600)  km-m-hr / km-hr-sec-sec

             =        0.324 m/s²      (rounded)

(This a rather gentle acceleration ... about 0.03 of a 'G' ...
so it would not mash you back into your seat in the car.)

As newton's first law states a object in motion stays in motion