Solve the following system by substitution -3x+y=-5 and 3x+6y=0

X+y=-4 x-y=2 use elimination with adding and subtraction

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.

Factor the polynomial expression x6 – x3 – 20