Since she wants you to use integers, you'll want to use 2 int member variables to contain the numerator and denominator. Then you can just override the tostring function to output them back in rational form.

As for the void function for arithmatic.

If a function is void nothing will get returned and anything done will be in that object only. I would assume this means she wants you to put the final value into the calling object. You may want to ask her to elaborate.

So if x = 1 and y = 1

then x.add(y) would make x = 2. so to output the result of the problem you would just output x.toString()

Having done this problem a few times in my programming classes, I would suggest the mainly overlooked part is to make sure you have a fuction to reduce the rational number to its lowest form. You can search the net a bit to find some good algorithms for doing this. Just make sure every time you do an arithmatic call, you reduce the result afterwards or you will end up with fractions like 6/12 when it should be 1/2.