There are 15 purple marbles, 3 pink marbles and 12 gray marbles. What is the ratio of purple marbles to all marbles?

Add the two expressions 3.8b - 7 and 2.9b + 9 enter your answer in simplified form

Explain how you can use the associative property to evaluate (7x50)x4.

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.