If 3log3^7 = x , what is the value of x?

With alll of except for the 2 that i did already

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.

Prove that 16^4-2^13-4^5 is divisible by 11.