Roy guessed that there were 15 baseballs in the bag, but when he counted, there were really 18. What is the percent error?

Based on what i know about mean, this doesn't add up.

Michelle had a birthday party. she bought a bag of candy with 96 starbursts, 72 hershey's, and 68 reese's. she wants to use all the candy she bought to make goody bags with the same amount of starbursts, hershey's and reese's in each bag. what is the largest number of bags she can make?

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days