How do you add and subtract rational numbers?

Answer 1

A rational number is a number of the form p/q where p and q are integers and q > 0.

If p/q and r/s are two rational numbers then

p/q + r/s = (p*s + q*r) / (q*r)
and

p/q - r/s = (p*s - q*r) / (q*r)

The answers may need simplification.