We have,
\(m _1=4\,kg , m _2=2\,kg , m _3=1\,kg\)
So,
\(4\,g =40\,N\) and \(2\,g +4\,g =6\,g =60\,N\)
So,
\(a _{ net }(\downarrow)=\frac{ f }{ n }\)
\(=\frac{60-40}{10}=\frac{20}{10}\)
\(=2\,m / s ^2\)
Thus, The acceleration of blocks will be
\(=2\,m / s ^2\)