The mean percentage of a population of people eating out at least once a week is 57% with a standard deviation of 3.5%. assume that a sample size of 40 people was surveyed from the population an infinite number of times. 95% of the sample mean occurs between % and %.

i am also doing this. 
you would have to remember to move the decimal enable to get normal numbers for the standard of deviation and mean.
so 

 then subtract and add that from your mean
the standard of error formula is = deviation/ the square root of the sample size then the confidence interval of 95% would have you multiply it by 2 or 2.02 for a more accurate result then you add and subtract that from the mean which would give you your answer
55.89 to 58.11

The answer to your question is i think 7