To write a fraction in simplest form, first we need to find the Greatest Common Factor (or GCF) of the numerator and the denominator.
The GCF of 26 and 39 is 13.
Therefore, we should divide both the numerator and the denominator by this number.
26 / 13 = 2
39 / 13 = 3
Therefore, 2/3 is 26/39 in simplest form.