\(\%^{63}_{29}Cu=x\%\)
\(\Rightarrow\%^{65}_{29}Cu=100-x\left(\%\right)\)
\(\overline{M}=\dfrac{63x+\left(100-x\right)\cdot65}{100}=63.54\)
\(\Rightarrow x=73\%\)
\(\%^{63}_{29}Cu_{\left(Cu_2O\right)}=\dfrac{73\%\cdot63}{63.54\cdot2+16}\cdot100\%=32.14\%\)