What is the complex conjugate of 13-21i?

Ineed with this problem 21 show steps

Need asap. solve for the following inequality

Scores on the cognitive scale of the bayley-scales of infant and toddler development range from 1 to 19, with a standard deviation of 3. calculate the margin of error in estimating the true mean cognitive scale score, with 99% confidence, if there are 12 infants and toddlers in a sample.