basics on laws of motion(HCV)

It shall be 20 kg wt.

Mathematically, One the right side say the tension in the string is T and on the left side it is T'.

Since, they aren't accelerating. Therefore,
LHS: T = 20g
RHS: T'= 20g

But since the spring balance in the middle is assumed to be massless, and hence the tension in all the parts of it would be uniform and equal (If we consider force pairs)

i.e., T = T' = 20 kg wt

thanks vivek....bt wht will be the reading of the spring bal.....

this was nt full sol.... i think there were sum more of it.....

Sum more.
TRY ZOOMING AND READ CALMLY. I hope it is readable.

Nice explanation Vivek [1]