The answer is 2/9. To simplify a fraction we must to divide both dividend and divisor by the same factor in order to get a prime number either dividend or divisor or both. So, both 6 and 27 are divisible by 3 and 6 divided by 3 is 2 which is a prime number. Thus: 6/27 = (6 : 3)/(27 : 3) = 2/9.