Could you please check my answers and units. Thanxs!

Question

1. An automobile starts from rest and accelerates at 3m/s2 for 4 seconds. How fast is it going after acceleration?
-I got 12 m/s

3. At time = 0 an automobile already traveling at 30 km/hr. accelerates at 3m/s2 for 2 seconds. During these two seconds, how far does it go?
-I got 12 m/s

4. An automobile is traveling at 30 km/hr. It accelerates at 3 m/s2 until it has covered 100 meters.. What is its new velocity?
- 6030 (not sure about units)

Answer 1

3. Change 30km/hr to m/s
30km/hr*1hr/3600sec*1000m/km

then
distance=vi*t + 1/2 at^2

Answer 2

4. You need to work the units. Chang 30km/hr to meters/second. Then work it, keeping the units in the problem until you find out what your answer is, numerically, and the units.

Answer 3

I am still not understanding. Like for number 3, this is as far as I got 30km/36000000. Then for number 4, would it be similar as to number 3? Also, did I get number 1 correct?