How can both the numerator and the denominator of a fraction increase and yet the fraction remains the same amount?

The important thing in a fraction is the relationship between the numerator and the denominator. Say there are four bran muffins on the table and you grab three of them. You have 3/4 of the total number of muffins. Now cut each muffin in half. You have six pieces and there are two on the table. You have 6/8 of the total of muffin pieces. The amount of muffin overall hasn't changed, nor has the amount you have.