Solve each of these equations using algebraic operations.
a. 2x - 10 = 4
b. 5-2x = 9
c. 6x + 3 = 5
d. 13 - x = 6
e. 12 - 3x = 11
f.4x - 3 = -11
8.15 - 2x = 1
h. 3(x + 1) = 11

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.