Your estimate of the baby pig's weight is 2 pounds. However the actual weight of it is only 16 pounds.
Let's solve for the percentage error of this.
=> 20 - 16 = 4 pounds
=> 4 / 16 = 0.25
=> 0.25 * 100% = 25%
Thus, you added 25% of the baby pig's weight
67 is a prime number, and its ones digit is two less than the tens digit.