For the first one, i think you have to use a t dist.
I get mean=40.929 and SD=72.131 and for 95% confidence interval i get 13.1065
For the second question they give it to you that its a normal since " the distribution of X is N(54.1, unknown )" The N infront of N(54.1, unknown ) means its normal
for the third question you just have to follow the equation given to you from the website you posted.
The fourth question look up type 1 and type 2 errors (sorry i can't remember how to do it)
The fifth i think is when that its highly skewed you can't rely on normal distributions but i might be wrong.