Acar accelerate from rest to a speed of 36 km/hr in 20 s . what is the acceleration of the car in m/s2?

The initial velocity is 0 (from rest) and the final velocity is 36 km/h

Average acceleration =  36 km/h - 0       36 km/h
                                      =
                                       20 seconds      20 seconds

We now convert 36 km/h to m/s as follows

36 km/h = 36 * 1000 m / 3600 s = 10 m/s 

Hence

Average acceleration =    10 m/s                       
                                      = 0.5 m/s squared
                                        20 seconds