Since it is a race, the runner start from rest, so we can use the Velocity Hourly Equation to describle yours moviment.
[tex]S=S_{o}+V_{o}t+ \frac{at^2}{2} \\ S=\frac{at^2}{2} [/tex]
Entering the unknowns, we have:
[tex]S=\frac{at^2}{2} \\ 12*2=a*4^2 \\ \boxed {a=1.5m/s^2}[/tex]
Number 2
If you notice any mistake in my english, please let me know, because i am not native.
