X, y, & z are letters, but in algebra, letters are referred to as?

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 radical expression is a rational number? a. √ 360 b. √ 644 c. √ 225 d. √ 122

Evaluate each expression. determine if the final simplified form of the expression is positive or negative -42 (-4)2 42