John is twice as old as mary. the sum of their ages is 21. how old is mary? let j = john's age and m = mary's age. select the system equations that represents the problem.
j - 2m = 0
m - 2j = 0
j + m = 21
j = m + 2

Acookie manufacturer advertised that every bag of a certain type of cookie contained at least 1000 chocolate chips. a consumer group bought 15 bags of cookies from a variety of locations, dissolved the cookies in water and hand-counted the number of chocolate chips in each bag. the average number of chocolate chips was 1161.6 and the standard deviation 117.6. a26. assuming a normal distribution, a 95% confidence interval for the mean number of cookies in each bag is (a) 1108.37 (b) 1108.13 (c) 1102.09 (d) 1096.86 to 1226.34 to 1214.83 to 1215.07 to 1221.11 (e) 1096.47 to 1226.73