Use Newton's Second Law: Fnet = ma
where Fnet = total net force, m = mass of object, and a = acceleration of object.
You are given Fnet = 26N and m = 4.0kg. Plug them into the equation and solve for a:
[tex]26 = 4.0a[/tex]
[tex]a = 6.5[/tex]
The answer is 6.5 m/s^2