What is the least common multiple of 42 and 9

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

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.

Which of the functions below could have created this graph?