The right question is
[tex]x ^{2} -8x=20[/tex]
now multiply 1/2 by the coefficient of x which is 8
[tex] \frac{1}{2} \times 8=4[/tex]
now add square of 4 on both side of equation we will get
[tex] {x}^{2} -8x+ {4}^{2} =20+ {4}^{2} [/tex]
[tex](x-4)^2=20+16[/tex]
[tex](x-4)^2=36[/tex]
taking square root on both sides
we get
[tex](x-4)=-+6[/tex]
[tex]x-4=6, x-4=-6[/tex]
[tex]x=6+4 , x=-6+4[/tex]
[tex]x=10,-2[/tex]
so third option is correct
if u find any confusion u can ask me
i hope you will understand it
Thank u
