How do you find the area of 12ft and 20ft and 18ft

Answer this question, only if you know the answer. 30 points and brainliest!

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.