In the figure, cd = ef and ab = ce. complete the statements to prove that ab = df.
cd + de = ef+ de by the
property of equality.
ce = cd + de and df = ef + de by
ce = df by the
property of equality.
given, ab = ce and ce = df implies ab = df by the
property of equality.

Ijust need these 2 questions answered (the second pic is just confirmation i'm not confident in that answer)

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.

An object in geometry with no width, length or height is a(n):