$\begin{cases}n_{NaCl}=x mol \\n_{CuSO_4}=y mol \end{cases}$Catot:
$Cu^{2+}+2e\rightarrow Cu$
$y 2y y$
$2H_2O+2e\rightarrow H_2\uparrow+2OH^-$
$2z z$
Anot:
$2Cl^--2e\rightarrow Cl_2\uparrow$
$x x 0,5x$
$\Rightarrow \begin{cases}0,5x=1,5z \\x=2z+2y\\58,5x+160y=51,1 \end{cases}\Rightarrow \begin{cases}x=0,6 mol \\ y=0,1 mol \end{cases}\Rightarrow \%m_{CuSO_4}=31,31\%$