We can assume that the horizontal surface has no friction and the pulley is massless. We can use Newton's second law to set up an equation.
F = Ma
F is the net force
M is the total mass of the system
a is the acceleration
a = F / M
a = (mb)(g) / (ma + mb)
a = (6.0 kg)(9.80 m/s^2) / (6.0 kg + 14.0 kg)
a = 58.8 N / 20 kg
a = 2.94 m/s^2
The magnitude of the acceleration of the system is 2.94 m/s^2
