Let 450N block moves down,

Consider the motion of 450N block,

Apply the equation, F = ma

450 – T = (450/9.81) a

450 – T = 45.87a ...(i)

Consider the motion of 300N block,

Apply the equation, F = ma

T - 300 = (300/9.81) a

T - 300 = 30.58a ...(ii)

Add equation (1) and (2) 150 = 76.45a

**a = 1.962m/sec**^{2 }

Putting the value of a in equation (i), we get

**T = 360N**