It works, but if you don't reduce it, you only get 1/2 credit.
LOL! Of course, if you find the appropriate common denominator, you are also not guaranteed to have a fraction in lowest terms. (Example: 1/3+1/6. Common denominator is 6, so 1/3+1/6=2/6+1/6=3/6=1/2.) By the way, in school you are taught to find the least common multiple of the denominators by factoring them. This works fine with small numbers, but truth be told, factoring numbers can be extremely difficult if they have more than several digits. The efficient way of finding the least common multiple of two numbers is to use something called the Euclidean algorithm, but this is not taught in grade school.