Answer:
95%
Explanation:
You want the percent of cookies having between 13.8 and 24.2 chocolate chips if the number of chocolate chips is normally distributed with a mean of 19 and a standard deviation of 2.6.
Z-score
The z-scores of these limits are found from ...
z = (x -µ)/σ
z = ((-13.8, 24.2) -19)/2.6 = (-5.2, 5.2)/2.6 = (-2, 2)
Probability
The empirical rule tells you that the percent of the distribution within ±2 standard deviations of the mean is 95%.
95% of the cookies will have between 13.8 and 24.2 chips.