What is the y-intercept of this line?

Perform the indicated operation. 8/a - 6/a + 7/a

What is negative 3/9 times negative 2/8 ?

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.