Did ari and cal walk the same distance?

Does anyone know how to do geometryme with this problem

In a graph with several intervals o data how does a constant interval appear? what type of scenario produces a constant interval?

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.