find out what the new given denominator (bottom number)/ numerator (top number) and divide the missing denominator/numerator by the number founded for the given numerator. in example: 3 people/9 pizzas. we are given the denominator of 3 pizzas and 9 divided by 3 is 3. so if the denominator is is dived by 3 the numerator must be divided by 3 as well. vice versa (same thing) if it was the numerator was given.
