Please help me solve 9 and 10 ASAP please

School has 204 sixth grade students. if the sixth grade is 30% of the total school, how many students are in the middle school?

Hi, can anyone show me how to do this problem? 100 points for this. in advance

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.