Two-thirds (which can be written as \( \frac{2}{3} \)) is equivalent to approximately 66.67% when converted to a percentage.
To find which of the options is equivalent to Two-thirds:
- 66 and one-third percent is \( 66.33% \).
- 66 and three-fifths percent is \( 66.6% \).
- 66 and two-thirds percent is \( 66.67% \) (this one is correct).
- 66 and \( \frac{7}{10} \) percent is \( 66.7% \).
Therefore, the answer is 66 and two-thirds percent.