Assuming that Nathalie's weight is still measured in pounds and ounces and that she has not lost or gained any weight since her birth, we can calculate her current weight as follows:
A) Nathalie weighs 7 pounds and 9 ounces at birth, which is equal to 7.5625 pounds. If she now weighs 12 times as much, she weighs 7.5625 * 12 = 90.75 pounds. In ounces, this is equal to 90.75 * 16 = 1452 ounces.
B) To calculate the percentage increase in Nathalie's weight, we need to first calculate the increase in her weight, which is equal to 90.75 - 7.5625 = 83.1875 pounds. We can then divide this increase by her original weight of 7.5625 pounds and multiply by 100% to express the result as a percentage: (83.1875 / 7.5625) * 100% = 1103.9%. This means that Nathalie's weight has increased by more than 1100% since she was born.