There are an infinite number of these fractions. They must be 1 and 1 in the numerator, and the denominator must be relatively prime to 2. The examples I have picked are prime in the denominator, but the rule is not without many exceptions. For example
1/9 + 1/9 = 2/9
I don't think you can pick an even denominator because it will reduce when put with two. Oh wait 2/18 + 2/18 = 4/18 = 2/9 But these could be reduced before adding. Still, it might count. It depends on who is marking the question.
What about an odd and even denominator?
1/9 + 1/18 = 3/18 = 1/6 There must be something that works, but I can't come up with an example.
