For multiplication, you can multiply both denominator and numerator seperately...EX:a/b*c/d=ac/bd For division, you can multiply the numerator with another denominator.. Ex:a/b divided by c/d = a/b*d/c=ad/bc For addition and subraction, first find the lcm of the denominators and then add/sub the numerators. Ex:a/b+c/d=(ad+bc)/bd.