Marco is incorrect. It is true that 2/3 is in simplest form and cannot be further simplified, however, 2/3 has equivalent fractions.
For example, multiplying both the numerator and denominator of 2/3 by 3 would result in 6/9. Therefore, 6/9 = 2/3 and is an equivalent fraction. 6/9 can be simplified to 2/3/