For adding, subtracting, and comparing fractions, it is suitable to adjust both fractions to a common (equal, identical) denominator. The common denominator you can calculate as the least common multiple of the both denominators - LCM(6, 12) = 12. In practice, it is enough to find the common denominator (not necessarily the lowest) by multiplying the denominators: 6 × 12 = 72. In the next intermediate step the fraction result cannot be further simplified by cancelling.
In words - twenty-three sixths plus three twelfths = forty-nine twelfths.
