A car accelerates from 25km/hr to 55km/hr in 30 seconds. What is its acceleration?
Convert the speeds to m/s, take the difference, and divide by 30 s.
That will give you the answer in units of m/s^2, which is probably what they want.
25 km/hr = 25*1000/3600 = 6.94 m/s
You do the rest