physics problem about tension

Net force acting on the system = (1x g) N = 10 N
where g is the acceleration due to gravity, taken to be 10 m/s2
Hence, acceleration of system = net force/total mass = 10/(4+2.5+1) m/s2
= 1.333 m/s2

Apply: net-force = mass x acceleration to the 1 kg mass
1g - T1 = 1 x 1.333
T1 = (g - 1.333) N = 8.667 N

Consider the 2.5 kg mass,
T1 - T2 = 2.5 x 1.333
T2 = (T1 - 2.5x1.333) N = 5.335 N

Consider the 4 kg mass,
T2 = 4 x 1.3333 N
hence, T2 = 5.332 N