Writing a fraction as a percentage means to transform the given fraction into an equivalent one, with denominator 100.
So, we want to write
[tex]\dfrac{2}{3}=\dfrac{x}{100}[/tex]
Solving for x yields
[tex]x=\dfrac{2\cdot 100}{3}=\dfrac{200}{3}=66.\bar{6}[/tex]