Newton's second law states: [tex]F=m*a[/tex]
F stands for force
m stands for mass
a stands for acceleration
Get a alone.
[tex]\frac{F}{m}=a[/tex] or [tex]a=\frac{F}{m}[/tex]
Plug in the values you have.
[tex]a=\frac{25N}{12kg}[/tex]
This gives:
[tex]a = 2.5\frac{m}{s^2}E[/tex]