Reducing Fractions/Entering fraction form

Is the only way to enter fractions in and scan them from the user is one number at a time as in, enter the numerator of fraction 1, enter the denominator of fraction 1 and have a scan statement in between those. I have my program written, but I couldn't think of a way to try and enter in one whole fraction at a time in the form, a/b. Also, how can I reduce the fractional answer? I have to write a program that adds two fractions, a/b + c/d. However, if the answer comes out, say 40/25 or 6/8, how could I write the code for reducing fractions. It has been a while since I have done any C programming and I have forgotten some of it.