As we know that acceleration is given as
[tex]a = \frac{v_f - v_i}{t}[/tex]
here we know that
[tex]v_i = 6 m/s[/tex]
[tex]v_f = 12 m/s[/tex]
[tex]\Delta t = 2 s[/tex]
now we will have
[tex]a = \frac{12 - 6}{2}[/tex]
[tex]a = 3 m/s^2[/tex]
so acceleration will be 3 m/s^2